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JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 353 Solid Sampling in Electrothermal Atomic Absorption Spectrometry Using Commercial Atomizers A Review Carlos Bendicho* and Margaretha T. C. de Loos-Vollebregt Laboratory of Analytical Chemistry Delft University of Technology De Vries van Heysfplantsoen 2 2628 RZ Delft The Netherlands Summary of Contents 1 introduction 2 Direct Solid Sampling 2.1 Atomization Systems 2.1.1 Graphite tube atomizer 2.1.2 Cup cuvette atomizer 2.1.3 L’vov platform techniques 2.1.3.1 Platform atomization 2.1 -3.2 Boat atomization 2.1.3.3 Microboat atomization 2.1.4 Cup atomizer 2.1.5 Cup-in-tube technique 2.1.6 Carbon rod atomizer 2.1.7 Graphite probe atomizer 2.1.8 Ring chamber atomizer 2.1.9 Second surface atomizer 2.2.1 Influence of particle size 2.2.2 Influence of sample homogeneity 2.2.3 Influence of sample mass 2.2.4 Influence of analyte location in the sample 2.2 Accuracy and Precision 2.3 Chemical Modification 2.4 Sample Introduction Systems 2.5 Sample Preparation 2.6 Calibration 2.7 Applications of Direct Solid Sampling 3 Slurry Sample Introduction 3.1 Preparation and Mixing of Slurries 3.1.1 Use of stabilizing agents 3.1.2 Magnetic stirring and vortex mixing 3.1.3 Ultrasonic agitation 3.1.4 Gas mixing of slurry 3.1.5 Pre-digestion of slurry 3.1.6 Electric dispersion in a condensed medium 3.2 Influence of Particle Size 3.3 Influence of Slurry Concentration 3.4 Chemical Modification 3.5 Calibration 3.6 Applications of Slurry Sample Introduction 4 Direct Solid Sampling Versus Slurry Sample Introduction 4.1 Sample Pre-treatment 4.2 Sample Introduction 4.3 Dilution of the Solid Sample 4.4 Sample Homogeneity 4.5 Peak Shape 4.6 Calibration 5 Conclusions 6 References Keywords Direct solid sampling; slurry sample introduction; electrothermal atomic absorption spectrometry; commercial atomizer; review * Present address Perkin-Elmer Hispania S..4. Calle La Mas6 2 28034 Madrid Spain354 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 1 Introduction The success of the technique depends on the skill of the The direct analysis of solid samples without chemical pre- treatment is a goal widely pursued in order to simplify the analytical procedure. The application of electrothermal atomic absorption spectrometry (ETAAS) to the direct analysis of samples is as old as the technique itself.' Electrothermal AAS has received increased attention for the direct determination of metals at trace levels in a wide variety of samples owing to its hgh sensitivity the simplicity of the instrumentation and the relatively low cost.Several reviews have addressed the solid sampling tech- nique from a general point of vie^,^-^ making reference to either specific ~ a m p l e s ~ - ~ or comparing different atomic spectrometric techniques.' Specific features of solid sampl- ing have been claimed throughout the literature. The advantages of using solid sampling over acid digestion or fusion procedures are obvious and they can be summarized as follows (i) reduced sample pre-treatment and hence an increase in the speed of the whole analytical procedure; (ii) low contamination risk an essential requirement when trace levels of metals are to be determined; (iii) fewer possibilities of analyte losses during the sample pre- treatment or retention by insoluble residues; and (iv) the use of corrosive and hazardous chemicals is avoided.The number of papers published between 197 1 and 1990 shows the impact of the solid sampling technique (Fig. 1). In this review attention is mainly focused on the literature concerning the application of commercially available atom- izers for solid sampling. Among the different procedures for inserting solid samples into the electrothermal atomizer two approaches are widely used firstly direct introduction of the solid sample and secondly the introduction of a slurry prepared by suspending the finely divided solid sample in an appropriate liquid diluent. The period between 1971 the year when the first application of solid sampling with a commercial atomizer was reported,8 and 1980 reflects the early development of the solid sampling technique.The applications reported for solid sampling were characterized by the use of laboratory- built atomizers capable of accepting solid samples wall atomization slow heating rates for atomization (ramp times of 1 s and longer) peak absorbance measurements and matrix-matched solid standards for calibration in addition to the use of unreliable and manually-operated sample insertion devices. analyst in many instances. I t is clear that problems and drawbacks arise when chemical pre-treatment is avoided.These problems are listed below. (i) Insertion of the solid sample into the atomizer is not as easy as it is for liquid samples. Direct introduction of the sample requires extreme care and training. Loss of sample and contamination can occur during the weighing andor transfer from the balance to the atomizer. This problem is less critical when using slurry introduction. (ii) A different weighing is required for each replicate in contrast to liquid samples which use direct insertion. This can make the analytical procedure tedious and clearly unacceptable for routine determinations. With slurry intro- duction several determinations can be performed using only one sample preparation. Some improvement has been achieved by the automation of solid sample introduction for routine determinations (see section 2.1.3).(iii) Problems arise with standardization that do not occur when working with liquid samples. Matrix depen- dence of the peak shape and incomplete release of the analyte from the solid sample are commonly found. Calibration with aqueous standards is only successful sometimes and the use of the standard additions method fails when the added analyte is not equally affected by the matrix. Calibration with certified reference materials (CRMs) of very similar matrix to the samples constitutes the most reliable approach. (iv) Chemical modifiers are less effective for the direct atomization of solids as the chemical modifier cannot effectively interact with the analyte which is occluded within the sample particles.Several solid chemical modifi- ers have been tried in order to improve this interaction. (v) Solid samples offer fewer possibilities for dilution when the concentration of analyte is high for which a decrease in the instrumental sensitivity or prior dilution of the solid sample with an appropriate solid buffer are required. The slurry technique allows dilution but critical use of dilution is required in order to avoid errors e.g. when only a few particles remain in the slurry. (vi) Precision is worse than for liquid samples. Typically relative standard deviations (RSDs) are about 10%. Preci- sion can be improved by either decreasing the particle size or increasing the mass used for the determination when sample inhomogeneity is the main factor affecting preci- sion.For many CRMs sample inhomogeneity has to be taken into account for sample masses of below 200 mg; this is much higher than the 0.1-10 mg used in solid sampling. (vii) Parts of the matrix can remain in the furnace after the atomization step and thereby cause the deterioration of the atomizer. The build-up caused by the matrix can also block the light beam emitted from the radiation source and hence affect the analytical performance. A cleaning-out step is necessary after a series of measurements in order to avoid this problem. (viiz9 Spectral interferences are more pronounced when the solid sample is atomized directly. High and structured background signals can cause large errors. The use of a powerful background correction system is required if accurate results are to be obtained.Oxygen ashing can also be helpful to remove non-specific absorbance interferences. (ix) Specific problems are associated with slurry intro- duction such as the need to maintain a stable and homogeneous slurry and contamination by the liquid (x) Problems arise when determining refractory metals owing to the incomplete release during atomization and OCClUSiOn in the solid matrix. Higher atomization tempera- tures are required to release the analyte in a reasonable period of time in comparison with liquid samples. 1970 1975 1980 1985 1990 diluent. Year Fig. I Number of papers published per year in the period between 1971 and 1990 in direct solid sampling (solid line) and slurry sample introduction (broken line) based on the 249 references included in the reviewJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL.6 355 (xi) Problems can arise in the preparation of blanks especially when using ground samples. Many of these problems have been partly solved during the last decade by the implementation of various new instrumental developments and by improving the analytical methodology. Progress in three different lines of develop- ment accounts for the present use of solid sampling as a reliable technique which is often preferred to the chemical pre-treatment of samples. These include the design of graphite atomizers specifically adapted to handle solid samples; the automation of solid sample introduction; and the use of stabilized temperature platform furnace (STPF) technology.The introduction in 1981 of improvements in furnace technology by Slavin and c o - w o r k e r ~ ~ ~ ~ ~ under the concept of STPF conditions can be considered as 'the break- through' allowing the solid sampling technique to become an alternative to the analysis of solutions in routine determinations. Although direct solid sampling has been widely docu- mented and reviewed no specific attention has been given to the introduction of slurries. The popularity of this technique as an alternative to direct solid sampling is reflected in the large number of papers published during the last decade (Fig. 1). In this review it is mainly commercially available atomizers that are discussed as laboratory-built atomizers have been extensively treated in previous review^.^-^ Direct solid sampling and slurry sample introduction are both reviewed independently so that the characteristic features of each approach can be easily overviewed; relevant applications are included.2 Direct Solid Sampling Early work reporting direct solid sampling showed that modifications to commercially available atomizers and the development of laboratory-built atomizers specifically de- signed for solid sampling were required. The main features of laboratory-built atomizers for direct solid sampling are (i) the use of larger dimensions than with the commercially available atomizers in order to facilitate sample introduc- tion thereby preventing the radiation beam from being blocked and avoiding a high background caused by the solid matrix; (ii) the separation of the volatilization and atomiza- tion of the analyte; (iii) the use of large sample masses in order to avoid errors caused by inhomogeneous distribution of the analyte; (iv) the lack of isothermality during atomiza- tion; and (v) the use of a low heating rate during atomiza- tion to avoid high background signals. The atomization of solid samples by using atomizers with larger dimensions than those used for liquid sampling was recommended by Langm~hr.~.~ Atomizers used for solid sampling can be heated inductively or resistively.Although resistively-heated furnaces are more common induction furnaces were designed to accommodate solid samples. Several manufacturers of electrothermal atomizers have implemented specifically designed atomizers for the direct analysis of solid samples.These designs include tube furnaces platforms cups and probes. Commercially avail- able atomizers are briefly described below. 2.1 Atomization Systems 2.1.1 Graphite tube atomizer Graphite tube atomizers are based on the Massmann design" (e.g. Perkin-Elmer and Varian). The solid sample can be introduced into the furnace either through a centrally located hole in the furnace or from the ends of the tube. Tube-type furnaces were widely used during the initial stage of solid sampling in ETAAS. In 1971 only two years after the introduction of commercial graphite furnace atomizers Kerbefl determined Au in polyester fibres by direct insertion of the sample. The problems associated with the use of this type of furnace include troublesome sample introduction; strong spectral interferences; and non- reproducible deposition of the solid sample on the wall.Accurate positioning of the solid sample is important in order to avoid non-reproducible vaporization as a result of the temperature gradient along the tube. 2.1.2 Cup cuvette atomizer In contrast to the Massman furnace the cup cuvette atomizer contains the sample in a cup-shaped furnace. This type of furnace is manufactured by Hitachi [Fig. 2(a)]. The main advantage of the cup cuvette atomizer is that the sample vaporization takes place slightly out of the absorp- tion volume so that blocking of the radiation beam as a result of the sample residue formed after atomization is avoided. In addition the cup cuvette atomizer gives reproducible sample deposition.Analytical applications using the cup cuvette atomizer have been reported by Takada and co-workers12-16 for the analysis of metals and alloys. Sensitivity can be improved by covering the cup cuvette with a graphite lid.'' The enhancement is due to an increased residence time of the analyte in the cup. 2.1.3 L'vov platform techniques L'vov et al.18 proposed the technique in which a platform made of pyrolytic graphite is inserted into the centre of a graphite tube. The sample is deposited on the platform. The platform is mainly heated by radiation from the hot tube wall. As a result a delay in sample vaporization takes place compared with the vaporization from the tube wall. Consequently the atomic vapour is formed when the gas temperature in the absorption volume has reached steady- state conditions. Isothermal atomization reduces both spectral and chemical interferences. Several electrothermal atomizers incorporate the platform technique for atomiza- tion.In all of them a graphite support of varying dimen- sions and relatively low mass is used. The temperature delay depends on the mass of the platform and the contact between the platform and the tube wall. Despite the extensive use of the platform technique for dissolved samples its application to solid sampling has been more restricted. Chakrabarti et d . 1 9 determined several metals in oyster tissue using wall and platform atomization and selective volatilization of the matrix. Although similar precision was found by using both techniques accuracy was better when the sample was atomized from a platform. Likewise platform atomization offered better sensitivity for volatile metals. Chakrabarti et made a comparison between wall platform and probe atomization for the direct determination of lead in bovine liver.Accurate results were only found with platform and probe atomization and by measuring the integrated absorbance. A special platform design has been reported by Brown et ~zl.,~' which facilitates the positioning of solid samples on the platform [Fig. 2(b)]. Kufurstz2 compared the different commercial atomiza- tion systems that are available for direct solid sampling. It was concluded that large graphite tubes are required in order to facilitate insertion of the sample and that L'vov platform conditions should be used for atomization.The manufacturers of graphite furnace atomizers supply a variety of graphite supports such as platforms boats and microboats which cause some delay in sample vaporization. However theoretical calculations indicate that the vapour phase temperatures reached with these types of atomizers are lower than for the L'vov platform atomizer and356 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 (a) Tube / Carbon Fig. 2 (a) Cup cuvette atomizer; (b) platform-tube atomizer designed by Brown el aZ.;2* (c) L'vov platform atomizer; ( d ) boat atomizer; (e) microboat atomizer; U miniature cup atomizer; (g) cup-in-tube atomizer; ( h ) carbon rod atomizer; (i) probe atomizer; 0) ring chamber atomizer designed by Schmidt and Falk;64 and (k) second surface atomizer designed by Rettberg and H~lcornbe~~ therefore increased chemical interferences can be ex- p e ~ t e d .~ ~ J ~ A brief description of commercially available platform atomizers is presented below. 2. I .3.1 Platform atomization. The L'vov platform sys- tem is supplied with the atomizers commercially available from Perkin-Elmer [Fig. 2(c)]. The mass of the platform is about 75 mg. The insertion of the platform into the tube is axial. Grooved and ungrooved tubes can be used to accommodate the platform. However this type of support is unsuitable for weighing the solid sample because part of the sample can be lost during the insertion operation although this system can be successfully used when the solid sample is introduced through the sampling hole of the tube by means of a solid injector.24 2.1.3.2 Boat atomization.The 'boat technique' is used in the atomizers manufactured by Grin Analysengerate. The behaviour of this system approaches that of the L'vov platform [Fig. 2(d)]. The deposition area (7 x 4 mm) is open and bordered. The boat has a mass of about 130 mg and is transferred from the microbalance used to weigh the solid sample to the atomizer by means of a special claw. Insertion is axial and is attained using a jerk-free mechani- cal guide. Sample masses of from 0.2 to 30 mg can be introduced with this system.25 An automated solid sample analysis system based on the boat technique has been developed.26 The AAS instrument includes a powder sampler an integrated microbalance and a transport and handling system for the sample boat.The applications reported for this technique include the analysis of metals and alloys,27 fly ash,28 sewage sludge,29 biological matter,3o p~lyethylene,~~ filter matter,32 marine foodstuff^^^ and salivary calculi.33 2.1.3.3 Microboat atomization. This technique is avail- able in the atomizers manufactured by Thermo Jarrell Ash. The microboat is a 6 x 4 mm and has an approximate mass of 120 mg. The deposition area is open and bordered [Fig. 2(e)]. The microboat containing the solid sample is trans- ferred into the atomizer in a similar way to the boat technique by using a special claw. The microboat is inserted into the graphite tube through a narrow slit. The insertion is radial and there is a low risk of contamination. A disadvantage of the microboat is that the delay in atomization is considerably reduced as the whole microboat surface is in contact with the tube wall.The microboat technique has been compared with atomi- zation using induction furnaces for the analysis of metallic ~ a m p l e s ~ ~ - ~ ~ and glass materials.37 Induction furnaces can only be operated at a maximum temperature of about 2600 "C which is 300 "C lower than that with resistively-heated furnaces. Resistively-heated furnaces permit lower charac- teristic masses to be obtained than do induction furnaces. In contrast to resistively-heated furnaces induction fur- naces allow the use of larger sample masses and hence lower background absorbances are produced.36 2.1.4 Cup atomizer The first application of a cup for solid sampling was reported by Price et a1.38 The use of graphite cups inserted into graphite tubes permits not only the safe transfer of sample from the microbalance to the atomizer but also facilitates its weighing.The sample introduction system ensures a reproducible sample-to-sample deposition and in contrast to the cup-in-tube technique (see section 2.1 S) the deposition can be viewed. The use of a cup for atomization also avoids deterioration of the graphite tube because there is no build-up of deposit on the wall.38 The cost is also significantly lower than that of the graphite tube. The cup atomizer is used in the electrothermal atomizers manufactured by Hitachi [Fig. 2m]. These atomizers use a miniature cup (2.5 mm diameter; 45 mg mass). The cups are inserted into the graphite tube through an enlarged hole in the middle of the tube; again a special claw is used for insertion.The risk of contamination is low but the area of contact between the cup and the tube wall is large and therefore the 'L'vov platform effect' is reduced. TheJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 357 reproducibility from cup-to-cup is sufficient to permit the use of one cup for each determination. The mass of sample that can be introduced ranges from 0.1 to 2 mg.39 Miniature cups used for solid sampling in the Hitachi atomizers are U- shaped in contrast to those used for dissolved samples. Atomization with graphite cups has been used for the determination of metals in particulate matter suspended in air,40 steel Cu and Cu alloys,41 stainless steel magnesite Mg-Zn alloys silica and Si-A1 alloys.38 Several applications for the miniature cup system have been reported such as the analysis of bovine plant matter,44 oyster and biological matter39 and marine organisms.46 The miniature cup has also been used to determine several metals preconcentrated from solution by coprecipitation with S-hydro~yquinoline,~~ dimethylglyoxime (DMG)-Ni- 1 -(2-pyridylazo)-2-naphthol (PAN)48 and magnesium 8- q ~ i n o l i n a t e .~ ~ The concentration factors achieved with preconcentration can be as high as 18 OoO-f~ld.~~ 2.1.5 Cup-in-tube technique The cup-in-tube atomizer for solid sampling is manufac- tured by Perkin-Elmer. In consists of a capsule that has an aperture of 3.5 x 4.2 mm and has a mass of approximately 180 mg [Fig.2(g)]. The capsule is radially inserted through a hole located in the middle of the graphite tube. There is some risk of contamination during the insertion or removal of the capsule from the tube. The delay produced with this system is significantly larger than that in wall or platform a t o m i z a t i ~ n . ~ ~ The reason for the pronounced delay is the larger mass of the capsule and the protection of the sample from radiational heating. The sample deposition is difficult to observe as the deposition area is closed. The gas above the sample is also shielded from radiational heating by the capsule walls. Gas and sample remain cold until the capsule is heated so that the heating mechanism of the sample is by conduction from the capsule wall.The characteristic masses obtained with the cup-in-tube technique are slightly worse than with the L’vov platf~rm.~’ Typically sample masses of 0.3-1.5 mg are i n t r o d ~ c e d . ~ ~ The applications of the cup-in-tube technique include the analyses of plants and plastic film,53 poly(viny1 chloride) (PVC) and bovine liver,51 coal coal fly ash and particulate matter,s2 biological matter54 and Ni-based alloys.5s 2.1.6 Carbon rod atomizer Carbon rod atomizers (CRAs) are open atomizers in which the sample is placed in a cup or tube which in turn is transversely heated by two graphite electrodes [Fig. 2(h)]. These atomizers manufactured by Varian were widely used for solid sampling e.g. for the determination of metals in particulate matter suspended in air.The air samples were filtered through cups or tubes made of porous graphite which subsequently were fitted in the atom- izer.56-58 A CRA can be operated under isothermal or non- isothermal atomization. Lundberg and F r e ~ h ~ ~ reported that isothermal atomization using a CRA with a cup offered better precision and accuracy for the determination of lead in steel and Ni-based . alloys. Lundberg60 indicated that integrated absorbance is preferable for measuring the atomic absorption signal even when the temperature of the carbon cup rises continuously during the atomization step and when using non-isothermal atomization. Precision was reported to be better when using integrated absorbance in comparison with peak height. 2.1.7 Graphite probe atomizer Probe techniques proved to be useful for isothermal atomization.A probe of graphite is inserted into a graphite tube that is pre-heated to atomization temperature [Fig. 2(i)]. This atomizer is commercially available from Philips. As the probe is primarily heated by radiation transfer from the hot tube atomization of the analyte takes place at a constant temperature of the gas phase. The probe technique has some advantages over the platform technique.20 In solid sampling the high matrix concentration can promote the removal of the atomic vapour from the atomizer as a result of the rapid increase in temperature. This can change the residence time of the analyte in the absorption volume. In probe techniques the temperature of the tube is constant when the sample is inserted so that this effect is minimized.More importantly probe atomization facilitates the dissoci- ation of molecular species. Probe atomization was used by Chakrabarti et aL61 for the determination of Pb Cd Ni Cu and Mn in airborne particulate matter by prior collection of the solid particles on the probe. Chakrabarti et uI.~O made a comparison between wall platform and probe atomiza- tion for the determination of lead in bovine liver. Reliable results were obtained with both probe and platform atomization. Probe atomization offers the advantage that drying and pyrolysis of the sample can be achieved outside the tube thereby eliminating some of the interferences caused by the matrix. Background signals caused by smoke condensation on cooler parts of the tube is also avoided.Schron et a1.62 used a graphite rod to insert solid geological samples into a graphite tube atomizer. Khammas et aI.(j3 reported the use of wall and probe atomization to deter- mine copper in milk powder. Wall atomization required the use of the standard additions method in order to obtain accurate results. In contrast however calibration using aqueous standards was feasible when probe atomization was used. 2.1.8 Ring chamber atomizer Schmidt and Falk64 designed a special graphite tube for direct solid sampling. The tube has rotational symmetry and a sample chamber that is isolated from the absorption volume [Fig. 20)]. The sample is accurately positioned owing to the tube configuration. Relatively large amounts of the solid sample (up to 10 mg) can be introduced.The ‘ring chamber tube’ does not have temperature gradients along the area where the sample is contained and it avoids blocking of the radiation beam. The metal vapour enters the absorption volume when the gas phase temperature is stabilized because of the small temperature gradient that occurs along the sample area and the short ramp time. This design was used to determine Au in gold wire for microelec- tronics and Cu and Ni in plant matter.64 2.1.9 Second surface atomizer Rettberg and H o l ~ o m b e ~ ~ achieved an effective separation between vaporization and excitation processes by condens- ing the atomic vapour on a cooled Ta surface (second surface atomizer). The system combines the use of a Ta plug onto which the analyte species condense and a tube-type furnace [Fig.2(k)]. Although the atomizer was originally used for liquid sampling,66 it is particularly useful for solid sampling because of the separation of the vaporization and excitation processes. The solid sample (0.7-4 mg) is weighed into a graphite cup using a microspatula and then the cup is placed in the tube and the Ta plug inserted. The tube is heated so that analyte vaporization and deposition on the Ta plug take place (transfer step). In contrast to the cup atomizer (section 2.1.4) the contact between the358 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 sample cup and the tube is good and consequently the temperature delay between cup and wall is small. During the transfer step the Ta plug is cooled by a gas stream in order to promote analyte condensation.Once the atomic vapour is deposited on the Ta plug the cup containing the sample matrix is removed from the tube (cool-down step). The Ta plug is inserted the cooling gas stopped and the tube heated to a high temperature so that the analyte is re- vaporized from the Ta surface. The atomic absorption signal is independent of the matrix and the background signal is low as a result of the separation of the analyte and the matrix during the transfer step. Recoveries are in the range 8 1 - 127% for citrus leaves fly ash river sediment and filter paper.65 A second surface atomizer was used by Rettberg and H ~ l c o m b e ~ ~ to measure the time-dependent vaporization rate of an analyte from an individual sample over several heating cycles.The data were related to the total amout of analyte in the sample using aqueous standards. The method was used to determine Pb in tin copper and steel?’ 2.2 Accuracy and Precision Apart from the errors that can arise during the weighing of the solid sample the transfer operation and the sample introduction there are also errors associated with direct solid sampling which depend on particle size homogeneity of the sample sample mass and analyte concentration. 2.2.1 Influence of particle size Most of the materials require grinding in order to reduce the particle size of the sample to an appropriate size (e.g. 5 pm). Grinding of the material is also recommended for solid samples that are originally in powder form when the analyte is non-homogeneously distributed. Grinding im- proves the contact between the surface of the atomizer and the solid sample.The grinding operation is not always easy to perform (e.g. for metallic samples) and requires great care in order to avoid contamination. For refractory materials such as rocks and minerals vaporization of the analyte is often influenced by particle size. Improved accuracy and precision have been reported when the particle size is reduced. Eames and Matousek68 observed a decrease of the sampling error in the determina- tion of silver in quartzite rocks when the particle size was decreased by grinding to less than 10 pm. In addition accuracy can be improved by grinding as the analyte is more readily released. Stoeppler et al.69 concluded that small sample masses yield low concentration values when the sample is insuffici- ently ground.There is some controversy in the literature about the influence of grinding of the solid sample. In several types of samples (e.g. biological matter) particle size has no influence on accuracy but only on precision whereas for refractory materials (rocks minerals etc.) vaporization of the analyte is often influenced by particle size. Takada and HirokawaI2 concluded that the surface area of the sample particles influenced the vaporization of the analyte. Integrated absorbance was measured for re- peated atomizations of the same sample until complete vaporization of the analyte was achieved. Frech and Baxter70 found that increasing the mass of the sample did not always cause a proportional increase of the atomic absorption signal.Calibration with aqueous standards for the determination of A1 in biological material was feasible provided that the mass of the sample was lower than 2 mg. Precision is poor when the sample is introduced into the atomizer as a single particle. Takada and Koide” indicated this problem in the determination of Cu preconcentrated using an ion-exchange resin and using wall atomization. 2.2.2 Influence of sample homogeneity The influence of inhomogeneity is more critical when the sample mass decreases (typically sample masses of 0.1 - 10 mg are used). The lowest sample mass that can be handled reflects the difficulty of weighing and introducing the sample into the atomizer. Lundberg and F r e ~ h ~ ~ studied the trace element distributions for metallic samples and con- cluded that the influence of inhomogeneity on precision was negligible even working with sample masses as low as 2 mg.Siemer and Wei73 also found that the homogeneity did not affect the precision for sample masses of about 1 mg when determining Pb in rocks and glasses. On the other hand the relative homogeneity of solid samples can be estimated from precision measurements and sample mass.69v70 For materials that display non-homogeneous distribution of the analyte precision can be improved by grinding. For a large number of solid materials the influence of homogene- ity is not critical for sample masses of less than 200 mg. 2.2.3 Influence of sample mass The sample mass introduced into the atomizer is related to the analyte concentration in the original solid sample.The range of sample that is suitable is determined firstly by the availability of a microbalance to handle small sample masses and secondly from the capability of the atomizer to accept larger sample masses. Several workers suggested using larger graphite tubes than those commercially avail- able in order to introduce sample masses of up to 200 mg. The use of larger sample masses mainly improves the precision especially for non-homogeneous samples. The range of the sample mass that can be introduced is limited. Although sample masses of approximately 1 pg have been sample masses of lower than 0.1 mg are difficult to handle i.e. to weigh and transfer. When the concentration of the analyte of interest is too high for the analytically useful working range of the calibration graph either less sensitive l i n e ~ ~ ~ J ~ dilution of the sample with graphite4ss68*7s-78 or increase of the internal flow of ArS3 can be used.However these procedures can be a source of error. Vapour phase temperatures are lower when an internal gas flow is used and therefore matrix interferences are enhanced. 2.2.4 Influence of analyte location in the sample Different types of bonding between the analyte and the solid matrix in addition to different locations of the analyte in the solid particles (i.e. on the surface or occluded within the solid particles) can influence the absorbance measure- ment because of different vaporization kinetics. One example was the determination of several metals in steel.Signals with double peaks were observed as a consequence of the occurrence of the two locations of the analyte in the steel grain.13 The formation of several peaks in the atomic absorption signals was also observed for the determination of Pb in plasticss1 using the cup-in-tube technique and was attributed to the way the plastic decomposed when the temperature was increased. Several peaks were observed when lead was atomized at low pressure from copper alloys which were ascribed to different chemical forms of Pb or changes in its location.79 2.3 Chemical Modification Chemical modifiers are used in ETAAS for several pur- poses.*O The addition of a suitable reagent to the sample can change the relative volatility of the matrix or analyte so that no interference due to the matrix occurs during the atomization step.Stabilization of the analyte by a chemicalJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 359 modifier avoids early losses that can occur during the pyrolysis and ramping steps of the atomization. Chemical modification for direct solid sampling is more complicated than for dissolved samples as the contact between the solid particles and the modifier is less effective. The addition of chemical modifiers has been used to diminish the volatility of the analyte to improve its release from the solid particles or to avoid the formation of double peaks. Chemical modifiers for direct solid sampling have been used in liquid and solid form. Chemical modifiers in liquid form are mostly used for the determination of highly volatile elements such as Pb Cd Se and As. The chemical modifiers most widely used are H3P0481 or H3P04 + (NH4)2HP0482 and HNO or HN03 + NH4H2P0421 for Pb; H3P0483 or NH4H2P04+HN0321~52 and H3P04 or Mg(N03)284 for Cd; HN03+Ni or HN03+Pd54 for Se; and H2S04+ HN03+Ni46 for As. Baxter and F r e ~ h ~ ~ reported that the use of Pd(NO& +Mg(N0,)2 rather than NH4H2P04 + Mg(N03)2 as a modifier for Pb and Cd determinations in solid samples gives superior results.In many instances a chemical modifier added in liquid form is ineffective for stabilization. de Kersabiec and BenedettiE4 carried out a study on the effect of chemical modifiers in liquid form including H3P04 Mg(NO& and Ni(N03)2 on the atomization of geological samples using the miniature cup and cup cuvette atomizers.Different samples were also atomized with the addition of chemical modifiers in the solid form. Double peaks were still obtained when liquid or solid modifiers were used. Graphite powder added to the solid sample is used to dilute the sample so that the mass of analyte atomized falls within the linear range of the calibration graph. In addition the graphite powder when mixed with the sample prevents the residue formed after atomization from fusing or sintering decreases chemical interferences and promotes the release of the analyte as the atomization occurs in a reducing environment.45~68.75-78,85,86 Moreover the lifetime of the atomizer is increased. Rapid deterioration of the surface of the atomizer was observed upon atomization of samples that contained large amounts of silicon.The silicon forms globules at high temperature which attack the pyrolytic graphite surface.68 The use of chemical modifiers in a solid form requires the modifier and sample to be ground and mixed so that the contact between them is good. Durnberger and co-work- e r ~ ~ ~ ~ ~ ~ found that Ni used as a finely divided powder was effective in stabilizing Se. It was essential that Ni was added in elemental form and in a 15-fold higher concentration compared with the amount used for liquid samples. 2.4 Sample Introduction Systems Four basic procedures have been used for sample introduc- tion in direct solid sampling. Firstly the introduction of a support on which the sample is weighed; once the sample is introduced into the atomizer the support is re-weighed.This procedure is used in most tube-type atomizers. The weighing and transfer operation requires care in order to minimize any contamination and possible sample losses. The Ta solid spoon commercially available from Perkin- Elmer belongs to this group of devices. The sample can be introduced through the dosing hole of the graphite tube provided the hole is enlarged.20 For solid samples consisting of ion-exchange resins used for preconcentration of metals from a solution a set of plastic tweezers and a small funnel can be used to introduce the resin particles into the tube.71 The second procedure a more advantageous approach is to use a graphite support for both weighing and atomiza- tion. Such systems are based on platforms boats micro- boats cups and probes as mentioned before.The use of inert supports made of ashless paper and cellulose acetate has also been attern~ted.,~ Inert supports tend to cause high blank values and moreover the residue formed after atomization can degrade the accuracy and reduce the lifetime of the atomizer. The third procedure involves the introduction of the sample by the use of special injectors. In order to facilitate the sample introduction through the sampling hole of the graphite tube solid sample injectors operated in a similar way to conventional autosamplers have been described. Grobenski et al.24 developed an injector to introduce fiiiely powdered samples into a tube-type atomizer. The injector works like a microsyringe and sample masses ranging from 0.5 to 5 mg were introduced.A different injector used for direct solid sampling was described by Kurfiurst et The reproducibility of the results is comparable to those obtained for manual solid sample introduction. The final procedure is the use of special sampling devices to collect the solid sample by filtration through porous graphite or electrostatic accumulation. These special sampl- ing devices are useful for solid materials suspended in gases.56-58,81-83 Collection on filters made of different ma- terials (ie. cellulose acetate or nitrate and PVC) has also been 2.5 Sample Preparation Sample treatment for solid sampling should be kept to a minimum in order to avoid possible contamination or loss of sample; although grinding sieving homogenization drying etc.are often required. Because of the influence of particle size on accuracy and precision grinding of the sample is carried out in order to convert the sample into powder form or to reduce the particle size. The grinding can be performed using agate mortars or vibrational pulveriz- ers. Grinding is suitable for brittle materials such as rocks minerals glass soils etc. Biological and vegetal materials can be converted into a solid that can be ground i.e. by drying dry ashing plasma ashing or Iyophilization. Grind- ing metallic samples is more troublesome and can cause contamination of the sample. 2.6 Calibration The solid matrix can strongly influence the shape of the signal obtained during atomization. This influence makes it troublesome to use peak height to quantify the atomic absorption signal.The fast transient signals require fast instrumental response and preferably integrated absor- bance meas~rements.~~ Calibration can be performed using several approaches (i) with CRMs; (ii) with synthetic solid standards; (iii) using the standard additions method; or ( i v ) with aqueous standards. The first approach requires appropriate CRMs to be available at the concentration level of the analyte of interest. This is not a general calibration method owing to the lack of reference materials with certified analyte concentrations covering the range of interest (e.g. for environmental samples). However calibration with CRMs has been used for solid sampling of metallic samples,92 sewage sludge,26 biological samples93 and plant It should be noted that a significant disadvantage of reference materials is that the certified concentration generally has an uncertainty which is large when compared with the measurement uncertainty of the method.Conse- quently the use of CRMs as calibrants will introduce a large and often ignored uncertainty in the final value. In some instances when CRMs are not available a synthetic solid sample that matches the composition of the original sample can be used.360 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 The standard additions method has been used to suppress the influence produced by the bulk composition of the solid sample. This method requires that the analyte contained in the solid sample and the added analyte are equally affected by the matrix.Three different approaches are possible for the standard additions method in combination with solid ~ampling.*~*~~ In the first approach increasing amounts of analyte are added to constant masses of solid sample. This is difficult to achieve as it requires weighing identical amounts of solid sample for each individual addition. The second approach involves the use of increasing masses of solid sample with the addition of constant amounts of analyte from a standard solution. In this approach only one standard solution is used and one addition is made and therefore the final result can be inaccurate. The third approach means varying both the solid sample mass and the standard additions amount. The absorbance signal is a function of two independent variables and can be extracted by multiple linear regression.The use of aqueous ~ t a n d a r d s ~ ~ - ~ ~ ~ ~ ~ requires that the absorption signal is independent of the bulk matrix and only dependent on the concentration of analyte. This requirement is usually not fulfilled because of both the spectral and chemical interferences caused by the matrix. For calibration with aqueous standards to be successful a set of instrumental requirements has to be met i.e. rapid signal processing integrated absorbance measurements Zeeman background correction and atomization under isothermal conditions. For solid samples the absolute calibration of the autosampler or pipette used to dispense the standard solutions is also important because the accuracy of the determinations is directly dependent on the accuracy of the pipette. 2.7 Applications of Direct Solid Sampling The applications of direct solid sampling in ETAAS are shown in Table 1.Applications are classified alphabetically with respect to the matrix. Information on the elements that are determined the type of atomizer used and the analytical performance are also given. Attention has been mainly focused on commercially available atomizers. 3 Slurry Sample Introduction The introduction of a suspension of the finely powdered sample (slurry) combines both the advantages of liquid and solid sampling.166 This technique was first used by Brady Table 1 Applications of direct solid sampling in ETAAS Sample Aerosols Airborne particulate matter Algal cells Alloys Alumina and synthetic Aluminium corundum Animal serum Biological matter Biological matter Element Pb Pb Mn Pb Fe Ni and Cr c u Ga Cr Cr Cr Co and Ni Pb and Ni Pb Pb and Cd Pb and Cd Hg Se c u As Cd Zn Pb Ba La and Mg Mn Cu and Cr A1 Mn TI Cd Pb Co Ni and Mo Atomizer Boat - Graphite tubet CRA (cup) Ta boat - Cup atomizer Graphite tube Graphite tube Graphite tube Graphite tube and PTS PT Boat Boat Boat Cup-in-tube Microboat and graphite tube Miniature cup CRA IC cuvetteg CRA Cup cuvette Cup atomizer Comments Atmospheric Pb is collected by membrane filters.RSD= 11-37% DL*=0.4 pg of Pb per filter-paper Freeze-dried sample RSD= 7% RSD = 20% RSD=2.6-16'41 RSD= 5.1-10.7% DL=0.18 ng DL=22.5 pg mg-l Lyophilysed sample. RSD=9-22Oh RSD= 5- 16% Introduction of 1 pg of tissue HN03 and NH4H2P04 as chemical modifier Study of homogeneity Air-dried and freeze- dried samples DL=O.15 pg g-l RSD= 9% for Ba; 1 7% for La; and 8% for Mg RSD= 10% for bovine liver and animal muscle Freeze-dried samples. - Coprecipitation in the cup with ammonium pyrrolidinedi thiocarbamatef Reference 95 90 96 59 97 85 98 99 100 101 74 21 102 103 30 54 104 39 105 70 106 107 108JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 36 1 Table 1-continued Sample Element Atomizer c u Miniature cup Comments Three solid standards (NET(/) are used for Calibration coprecipitates with magnesium oxinate and DMG-Ni-PAN Pb and Cd profiles are determined in birds' feathers - Solid sampling and wet digestion are compared Deuterium and Smith- Hieftje background correction are compared Reference 93 109 110 1 1 1 112 113 24 114 44 49 115 94 116 117 Pb and Cd Boat A1 Cup-in-tube Cr Pb Cd Boat Cd Boat Ni and Hg Biological and vegetal matter P Graphite tube Pb Rb Cd Cu PT Ni and Mn Nine elements Boat Pb Cd Mn Cu Zn and Cr Al Cd Co Cu Mn Ni Pb and Zn Miniature cup Miniature cup Peak area.Special injector is described Coprecipitation with magnesium 8-quinolinate. Multi-element analysis - Generalized standard additions method for calibration Automated introduction - CRA Al Ag Ni and Se - Pb Cd Zn Mn and Se Cup atomizer Probe technique c u Ni and Ag chemical modifiers are attempted. For Se calibration with solid standards is required also freeze-dried samples Direct introduction and 118 Pb and Sb - Biological matter from a river ecosystem Cu Pb Cd and Zn Boat Biological matter and marine organisms As Miniature CUD 119 RSD= 3- 10% Standard additions method RSD = 5.5- 13%.Aqueous for calibration standards for calibration RSD = 9.6% RSD = 6.3-7.3% DL=5.1 pg graphite. RSD = 4.9% additions method for calibration Ni Calibration with aqueous standards is well suited for Pb and Zn but not for Mn. RSD= 514%. Pipette method for sampling Sample mixed with RSD = 10%. Standard RSD = 10% for Cd; 10-20% for Dilution with graphite. 46 120 Bovine liver Cu Zn Pb Co Fe and Cd Pb Graphite tube Graphite tube. and PT PT and probe 20 Cd Pb Miniature cup Miniature cup 42 43 Calcium carbonate Coal cu Miniature cup 121 Be Graphite tube 122 Cd and Ni Pb Zn and Mn Cup-in-tube 52 123 Cup cuvette Coal and particulate matter Coal and petroleum coke Copper Se Boat DL=O.l pg g-I RSD = 7-2 1 '/o Standards are prepared by quantitative doping of high-purity Cu 77 Cu Ni and V Ag Boat Graphite tube 124 92 Fibre and plastic paper Filter material Fly ash Freshwater mussels Cu Fe Mn and Si Cd Boat TI Boat A] Cr Cu Pb and Graphite tube Graphite tube Zn 125 126 28 I27 - - - Freeze-dried samples362 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL.6 Table 1-continued Sample Gallium arsenide Geological samples Glass Graphite Hair Hair Inorganic samples Ion-exchange beads Malt and yeast Margarine Marine foodstuffs Metal and alloys Metals (Ta Fe and Metals and oxides Nickel-based alloys Fe-W) Oyster tissue Paper Particulate matter Pancreatic tissue Pancreatic tissue Pancreatic tissue Petroleum Phosphorized Cu alloy Pig liver Plankton Plant and biological matter Plant matter and oyster mussels Element Cr Cr As Cd Pb Hg Sb and Se Ag Pb and Bi Pb Pb 13 elements Cu Ag Coy Ni and Pb As Cd Cr Hg and Pb Pb and Cd T1 Ni Cd Pb and Hg Bi Pb Ag and Te Ca Several Pb Bi Se and Te As Sb Se and Te Cd In and Zn Pb T1 Bi Te Se and Pb Cd Pb Zn Cu Co and Fe Cd Hg Cu and Cr 10 elements Pb Be Cd Se Ag Hg Pb Hg Pb Be and Cd Cd Hg and Cu Ca Cd Cd Be Pb Pb Cd and Zn Cu and Cr Pb and Cd Cr Atomizer Comments Graphite tube - miniature cup and PT study - - Cup cuvette Chemical modifier Microboat and Cup cuvette induction furnace Graphite tube Graphite tube Boat - Cup-in-tube Boat Boat Microboat and induction furnace - Boat Graphite tube and Microboat and CRA induction furnace Microboat and induction furnace Cup-in-tube Graphite tube Boat CRA CRA (cup) CRA (CUP) CRA (CUP) CRA (tube) CRA (tube) Cup atomizer Boat Graphite tube CRA Graphite tube and CRA Graphite tube Boat Graphite tube Cup-in-tube - Miniature cup Dilution with graphite. DL=0.03 ng of Pb DL=O.Ol pg g-' Dry ashing followed by atomization Silk and animal hair are used as solid standards - Signal summation method is used to improve the signal-to-noise ratio.Calibration with aqueous standards is feasible - Sample is a chip of the metal DL= 50 pg of Ca - RSD=7-25'h DL=O.l 0.1 0.06 and 0.003 pg g-' for As Sb Se and Te respectively RSD= 12% for Zn 8% for Cd and 7Oh for In. DL=10 2 and 10 ng g-l for Zn Cd and In respectively Calibration with standard additions method.DL=0.5 pg g-' of Pb RSD = 4.9Oh Calibration with aqueous standards and use of chemical modifiers. RSD=6-14% Peak height. Standard additions method for calibration - - RSD=4.2Oh RSD = 1 5% - RSD = 7- 1 4Oh RSD = 6Oh Collection on filter Collection on filter. RSD = 1 Ooh RSD = 14.8Oh - - DL= 1 ng g-I of Be (HGA) and Atomizer is modified 10 ng g-I of Be (CRA) for vacuum atomization - Pd +magnesium nitrate is more suitable than NH4H2P04+ magnesium nitrate DL=7 pg RSD=6-9% Reference 128 129 84 37 130 131 132 133 76 134 135 136 25 34 137 27 138 35 36 139 55 19 140 141 81 56 83 57 58 40 32 142 143 144 145 79 146 147 23 45JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 363 Table 1 -continued Sample Element Atomizer Comments Reference 50 148 53 51 8 31 149 150 151 152 71 153 154 82 73 38 155 33 47 86 28 26 68 75 156 157 13 12 60 158 159 160 72 41 15 16 17 14 161 77 162 163 Plant soil As Cd Cr Cu Pb and Mn Pb Cu Cd Mn and Rb Cup-in-tube CRA Cup-in-tube Cup-in-tube Graphite tube Boat Graphite tube CRA Boat RSD = 1 0% Plastic RSD= 15% RSD = 3.1 - 1 2% Plastic film PVC Polyester fibre Polyethylene Polymers PVC air filter Rat placenta and bovine liver Cr Pb and Cu Au Pb Cu Cr and Ni Fe Cu and Cr Be Cd RSD = 4-6% DL=0.02 pg g-' - Freeze-dried sample.DL=0.005 ng Comparison of microwave digestion and direct solid sampling. Samples were diluted with urea RSD=4.1% RSD= 10-20% RSD= 10-20% O2 ashing Red mud Cd Cr Pb Ag and PT Au Resin (cation-exchange) Cu Graphite tube Rocks and sediments Rock samples Cd Graphite tube Au and Ag CRA Pb PT Rocks glasses and Rocks and alloys Sediment soil fly ash leaves and water Pb CRA (cup) Pb Na Fe and Ti Cup atomizer RSD = 8% Pb Cd and Cu Boat Digestion is recommended for soil and solid sampling sediments and leaves Salivary calculi Sea-water Cd Pb and Zn Boat As Cd Zn Pb and Miniature cup Zn I Preconcentration with 8-hydroxyquinoline.RSD=6-14% Several NIST and BCR standards Pb and Cd Cup-in-tube Pb Cd and Hg Boat Cd Boat Ag CRA (cup) and boat Study of homogeneity Sewage sludge - Automated system Dilution of sample with graphite. RSD=8.l% Dilution with graphite Aqueous standards for calibration O2 ashing Study on double peaks DL=0.1 0.04 and 0.008 ng of Cu Mn and Ag respectively - RSD = 3.840% Silicate rocks Siliceous materials Ca Mg and Fe Ta boat Silicon Pb Sb and Mn Microboat Spinach Steel Rb Graphite tube Pb Bi Ag and Zn Cu Mn Ag and Pb Cup cuvette Cup cuvette Pb CRA Ag Bi Cd and Zn Pb and Bi CRA CRA (cup) Steel and Ni-based alloy Steel Fe-Mo and Ni-based alloy Steel Cu and Cu alloy Tin Pb Bi Zn and Ag Microboat RSD = 6% Pb and Sb Graphite tube Pb Cup atomizer Zn and Bi Cup cuvette Pb and Cd Cup cuvette DL=34 ppb RSD = 3.6-9% for Pb and Sensitivity is RSD = 9-43% 5- 12% for Cd enhanced by covering the cup with a lid RSD= 6-28Oh RSD = 7-9% RSD= 7- 12Oh Pb Cup cuvette Tin ingot Uranium oxide (U,O,) Cu and Ag Cup cuvette Cd and Li CRA Co Cr Cu Mn and CRA Ag Ca K Li Mg CRA c o Miniature cup Ni Na Pb Sn and Zn Vitamin B12 Calibration with a synthetic reference material.DL= 0.15 ng ml-1 of Co or 4 ng mg-I of vitamin B12364 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1 99 1 VOL.6 Table 1-continued Sample Element 'Atomizer Comments Reference Water co Miniature cup Sample was mixed with 164 20 mg of Mg and 2% 8-hydroxyquinoline (2-5 ml) for preconcentration Water borne Water samples Cd Cu Mn Pb and Miniature cup Coprecipitation Wheat particulate matter Cd Pb and Cu Boat - Zn with DMG-Ni-PAN Cd Boat - * DL detection limit. f Graphite tube heated graphite atomizer (HGA) and graphite tube atomizer (GTA). $ PT atomization with L'vov platform. 9 IC cuvette integrated contact cuvette. fi IUPAC name ammonium pyrrolidin- 1 -yldithioformate. )I NIST National Institute of Standards and Technology [formerly known as NBS (National Bureau of Standards)]. 89 48 165 and c o - ~ o r k e r s ~ ~ ~ J ~ * to determine Zn and Pb in leaves and marine sediments.The slurry technique overcomes some of the problems associated with direct solid sampling as it permits sample introduction using micropipettes and auto- samplers which are routinely used in liquid sampling. Another remarkable feature of slurry introduction is that the same atomizers that are used for liquid sampling can be successfully used for the atomization of slurries. Most of the work done in slurry sampling has been carried out using wall atomization and platform atomization with tube-type atomizers. The most critical factor in the slurry technique is probably the need for maintaining a stable slurry during the time required for sample introduction. So far homogeniza- tion procedures include the use of stabilizing agents magnetic and ultrasonic agitation vortex mixing gas mixing and pre-digestion of the slurry.The particle size of the solid sample can have a strong influence on accuracy and precision. Successful slurry analysis requires the char- acterization of (z] the sample homogeneity; (ii) the grinding and sieving; (iiz] the preparation of the slurry (i.e. the liquid medium by the addition of chemical modifiers and wetting agents and antifoam agents); (iv) the mixing and homogeni- zation of the slurry (i.e. the use of stabilizing agents or agitation systems); (v) the extraction of analyte into the slurry medium (i.e. influence of the acidic diluent and efficiency of the agitation system in achieving extraction of the analyte); (vi) the influence of particle size on deposition of the slurry sub-sample (i.e. the concentration range of the slurry required to obtain reproducible and representative sampling; and (vii) the influence of particle size on atomization efficiency (i.e.the determination of the rela- tive atomization efficiency for the slurry sample and the possibility of using aqueous standards for calibration). 3.1 Preparation and Mixing of Slurries Preparation of the slurry consists of adding a liquid diluent to the solid material that has been previously ground and sieved (when necessary) weighed and placed into a con- tainer in which the slurry is stable during the time required for sampling. The amount of solid material that is weighed depends on the concentration of the analyte and the dilution in the final volume of the slurry.For samples of low homogeneity the precision is improved when larger amounts of sample are used to make the slurry. The introduction of the slurry sub-sample into the atomizer can be carried out manually or by using an autosampler. When autosampler cups are used in the weighing of the solid material the maximum volume of slurry is limited to the cup volume (about 2 ml) which in turn limits the maximum amount of material that can be suspended. Once the slurry is prepared the solid sample must be equally distributed in the volume of the liquid. The different approaches available to maintain a stable and homogeneous slurry are discussed. 3.1.1 Use of stabilizing agents Slurry preparation in aqueous solution is rarely suitable because most powdered materials undergo rapid sedimen- tation.Sedimentation of the suspended material usually occurs after mixing the slurry and can be quantified by using Stoke's law. The sedimentation rate depends on the densities of the diluent and solid material the viscosity of the diluent medium and the radius of the sample particles. The slurry can be stabilized using a highly viscous liquid medium. So far gly~erol,l~*J~~ non-ionic surfactants' 74 and organic solvents of high have been used as slurry stabilizing agents. The stabilization capability of these reagents largely depends on sample characteristics and particle size. As pointed out by Majidi and H o l ~ o m b e ~ ~ ~ the time interval between complete mixing of the slurry and the removal of an aliquot for analysis can be increased in a highly viscous medium with a density similar to that of the particles.Fuller and Thompson169 used a thixotropic thickening agent to stabilize slurries prepared from rock samples. The procedure consisted of the addition of sodium hexameta- phosphate as wetting agent and ammonia to neutralize the medium. The slurry was stable for several days. Stabilizing agents are useful when an autosampler is used to introduce the sample as the slurry can be left in the sampling cups without further homogenization. 17* Little- john et all7' observed that the stabilization of the slurry was dependent on both the particle size and the concentra- tion of the stabilizing agent. Sample deposition was difficult owing to the high viscosity of the medium when the Viscalex concentration was greater than 2-3Oh.On the other hand the maximum slurry concentration to be used depends on the concentration of the stabilizing agent. Stephen et ~ ~ 1 . l ~ ~ found that the maximum slurry concentration was 10% when a stabilizing agent concentra- tion of the order of 3Oh was used for slurries prepared from a spinach sample (50 pm particle size). Similar behaviour was observed when glycerol was used as the stabilizing agent. Problems are reported with respect to the use of viscous media in slurry preparation. The sample aliquot is ineffici- ently pipetted into the atomizer when the concentration ofJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. AUGUST 1991 VOL. 6 365 the stabilizing agent is high.The sample can remain around the dosing hole which can degrade the precision. This problem has been observed using mi~ropipettesl~~ and autosamplers.166 The use of an autosampler also requires a cleaning procedure for the capillary between each of the successive determination~.'~~J~~ It is also necessary to add an additional pyrolysis step in order to remove the excess of stabilizing agent. 169~172 Stabilizing agents are usually ineffici- ent when the slurry contains particles of high density.177 It has been reported that glycerol causes interference for Cd and Pb even under isothermal atomization condi- t i o n ~ . ' ~ ~ Owing to the carbon build-up formed on pyrolys- ing the glycerol both Cd and Pb absorption signals shifted to lower temperatures which caused non-isothermal atomi- zation.These problems can be minimized by cooling the slurry to 5 "C and using the smallest amount of glycerol possible in order to reduce the interference. Apart from stabilizing agents the addition of wetting and antifoaming compounds can improve the dispersion of the slurry. The application of wetting and dispersive additives was discussed by Tsalev et a1.80 in an extensive review on chemical modification in ETAAS. In slurry analysis Triton X-100 is useful to disperse solid particles that might otherwise tend to float on the top of the l i q ~ i d . ' ~ ~ J ~ ~ Viscous samples containing solid particles (for example petroleum products) can be sampled as a slurry. Dilution with an organic solvent is required to reduce the viscosity so that sample introduction is facilitated.l g 0 3. I .2 Magnetic agitation and vortex mixing Magnetic agitation and vortex mixing have been widely used mainly during the early work carried out using the slurry technique. Slurries are prepared in a beaker and the slurry is stirred in order to achieve a homogeneous distribution of the solid material (usually for 3-5 min). The stirring action is stopped and a sample aliquot is withdrawn and introduced into the atornizer.lg1 The sample aliquot can also be withdrawn under continuous stirring.lg2 The effectiveness of magnetic stirring and vortex mixing basically depends on the sedimentation rate of the sus- pended material. Hinds et allg3 reported that differential sedimentation of sample particles produced during work with soil samples contributed to an incomplete recovery of Pb.The error associated with sedimentation is a function of both particle size and the presence of particles having different composition. As a result large errors can be expected when the analyte is predominantly distributed in particles of high density which undergo rapid sedimentation. Miller-Ihli 73 compared vortex mixing with ultrasonic agitation systems for the homogenization of slurries for ETAAS. The precision achieved with these systems was not significantly different. However vortex mixing caused lower recoveries of Fe. After magnetic agitation or vortex mixing slurries are usually introduced with a micropipette because of the difficulty of incorporating these systems in an autosampler. Lynch and LittlejohnIs4 reported a miniature magnetic stirring device that could be used in combination with an autosampler.Slurries were homogenized in the autosampler cups using small magnetic bars coated with polytetrafluoro- ethylene (PTFE). The system showed good performance for the determination of Pb in freeze-dried samples. 3.1.3 Ultrasonic agitation Ultrasonic agitation has been used as an effective system to homogenize slurries for ETAAS. Ultrasonic agitation can be used in combination with both manual and automated introduction of the slurry. An advantage of this system in comparison with magnetic agitation and vortex mixing is that the analyte of interest is partly extracted into the liquid phase owing to the ultrasonic action when the slurries are prepared in an acidic medium.Ultrasonic agitation is more effective than other agitation systems. This is important when the analyte is predominantly located in the larger sample particles that undergo rapid sedimentation. Miller- Ihli173 reported obtaining improved recoveries for the determination of Fe in wheat flour and bovine liver when the sample was sonicated. Agitation with a small ultrasonic probe also permits the slurry to be prepared directly in the sample cups of the autosampler. van Loenen and reported the modifi- cation of an autosampler in order to use ultrasonic agitation of a slurry prepared from coal fly ash samples. They reported that ultrasonic stirring could not maintain a homogeneous slurry during the time required for the autosampler to withdraw the sample aliquot unless com- plete analyte extraction was achieved.Preparation of the slurry outside the autosampler cup permits work with larger sample masses than those used when the slurry is prepared directly in the sample cup (200-300 mg versus 1-2 mg) which facilitates the work with less homogeneous samples. The ultrasonic treatment of slurries requires special care in order to avoid contamination when the titanium probe touches the wall of the cup. The leaching of metallic impurities from the cup wall has been observed with polyethylene cups but not with PTFE cups.173 Miller-Ihli18s automated the system combining ultra- sonic agitation and sample introduction with the autosam- pler. A similar design has been reported by Carnrick et and is commercially available from Perkin-Elmer.Auto- matic slurry sample introduction in combination with ultrasonic agitation has been used by Epstein et to study the sources of variability in the measurement. It was concluded that the precision depends on both the extraction yield of the analyte and the homogeneity of the sample. Precision of 2-1Oo/o was obtained by Bradshaw and Sla- vinIB8 when determining Se Pb and T1 in coal and coal fly ash. The time required for each determination was less than 1 min by using ultrasonic agitation of the slurry and elimination of the pyrolysis step. This method was also used to determine Mn.IB9 3.1.4 Gas mixing of slurry Bendicho and de Lo~s-Vollebregt~~~ reported a procedure in which effective homogenization of the slurry was achieved by passing an Ar stream through a narrow capillary tube introduced into the slurry medium.This system allows sample preparation directly in the cups. The homogeniza- tion requires a 'bubbling time' with the Ar stream of only 30 s. The precision obtained for the determination of Cu Co Cr Mn Fe and Ni in different samples of glass was about 6%. This system is easy to handle and it does not require the use of stabilizing agents or special devices for agitation. However the effectiveness of mixing largely depends on both the particle size and the characteristics of the solid sample. 3.1.5 Pre-digestion of slurry Pre-treatment of the slurry can be helpful to extract the analyte of interest into the liquid phase. In contrast to the extensive sample pre-treatment inherent in fusion and digestion procedures that are conventionally used pre- digestion of a slurry only requires a partial decomposition of sample hence it is not time-consuming.Fagioli and co- w o r k e r ~ ' ~ ~ - ' ~ ~ were the first to use partial wet oxidation of several biological and vegetal materials by concentrated sulphuric acid and subsequent analysis of the carbonaceous366 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 slurry thus formed. This method is much faster and more reliable than those based on dry ashing or extensive wet oxidation. Slurry pre-digestion can also be accomplished in the sample cups of an autosampler. Hoenig et ~ 1 . l ~ ~ reported the difficulties of stabilizing slurries containing large par- ticles in the analysis of sediments and particulate matter. In order to solve these problems pre-digestion was performed by adding a small amount of concentrated nitric acid to the sampling cups containing the slurry. Partial extraction of the analytes into the liquid part of the slurry was obtained.The pre-digestion step significantly improved both the precision and accuracy. A rapid pre-digestion procedure has been proposed by Bendicho and de L~os-Vollebregt~~~ for the determination of several metals in glass. Pre-digestion of the slurry was based on the addition of hydrofluoric acid at a low concentration (3%) and homogenization by gas mixing.177 The pre-digestion step is accomplished in the sample cups of an autosampler 3 min being sufficient to achieve an effective extraction of the analytes from the powdered glass (15 pm particle diameter).This approach gives 2-fold improvement of precision for the determina- tion of Cu Co Cr Mn Fe and Ni in comparison with that obtained without pre-digestion. Cold extraction using di- lute hydrofluoric acid is found to be useful for those materials in which the analyte is predominantly contained within the siliceous fraction. 3.1.6 Electric dispersion in a condensed medium The electrical dispersion of metallic samples in a condensed medium gives rise to a colloidal suspension which is suitable for the slurry technique. Pchelkin and co-work- ers19591% studied in detail the characteristics of the sols formed upon spark ablation. The colloidal suspension contains metallic particles with particle sizes of less than 1 pm and displays high stability.Using this method slurries of metallic materials are obtained without the need for machining in order to convert the sample into a powder and therefore there is a reduced risk of contamination. The spark ablation can be performed in aqueous and organic solvents. This method is attractive for metallic samples that are difficult to dissolve by conventional acid digestion. 197 3.2 Influence of Particle Size The particle size of the solid material used to make a slurry can influence the stabilization deposition and atomization efficiency of the slurry which in turn can influence both accuracy and precision. Fuller et reported that the precision achieved for slurry sample introduction was largely influenced by particle size although this was not a critical factor in achieving effective atomization.Relative atomization efficiencies of about 100% were obtained for the determination of several metals in titanium ores and silicate rocks provided that the diameter of the solid particles was less than 25 pm. Under those conditions calibration could be carried out using aqueous standards. The decreased influence of particle size on atomization is an advantage of ETAAS over other atomic spectrometric techniques used in combination with slurry sampling such as flame AAS and inductively coupled plasma atomic emission spectrometry. Several workers have reported quantitative recovery of the analyte for particles of signifi- cantly larger diameter (25 pm). Hinds et ~ 1 . ~ ~ ~ reported incomplete recovery for lead when determined in soil; owing to the slower vaporization of the larger particles Pb is inefficiently atomized within the observation time.Pipetting efficiency was only 80% when the particle size was larger than 50 pm. Inefficient atomization was observed unless the particle size was between 50 and 2 pm. Karwowska and Jackson199 used solid samples with particle sizes of less than 20 pm during their atomization studies of Pb from a synthetic soil matrix to obtain better precision. In contrast Miller-Ihli173 pointed out that the precision achieved was better for particles in the range 250-600 pm in comparison with the precision achieved with small particles. Stephen et aL2O0 found improved precision in the analysis of liver tissue when the finest fraction of the sample (particle diameter less than 21 pm) was used.Chen and Xuzo1 established that particle size should be lower than 76 pm in order to obtain quantitative recoveries when deter- mining trace metals in aluminium oxide. It is obvious that smaller particles facilitate sample preparation and improve recovery. Errors associated with large particles (diameter > 100 pm) arise from the difficulty of maintaining a homogeneous distribution of the large particles in suspension and the lower pipetting efficiency for large particles. Grinding of the original sample is usually required in order to minimize the errors. The optimum range for particle size depends on sample composition. 3.3 Influence of Slurry Concentration Another important factor in the slurry technique is the slurry concentration.Samples of high analyte content can be analysed more readily by the slurry technique than by direct solid sampling as the slurry can be easily diluted. However dilution of the slurry can only be carried out within a limited range; precision is degraded when working with highly diluted slurries because only a small number of particles remains in the slurry. On the other hand when the analyte content of the original sample is very low the concentration of the slurry can be increased accordingly although pipetting efficiency can deteriorate if slurries are more concentrated. Another factor to be taken into account is the increase in the matrix effects that can arise when the slurry concentration is increased. Lynch and L i t t l e j ~ h n ~ ~ ~ established an optimum slurry concentration range for the analysis of food.Precision was less than 4% when working with particles of less than 50 pm in diameter provided that the concentration of slurry was below 10% m/v. The accuracy deteriorated when the slurry concentration was above 5% as a result of the excess of matrix. Slurry concentrations higher than 5% caused inefficient deposition of the slurry aliquot. Holcombe and MajidiZoZ characterized the errors associ- ated with slurry sampling. Errors can arise from uncertain- ties in the sample volume the number of particles in the sample volume and the variation in the mass of the individual particles. It was concluded that errors can be minimized by working with small particles concentrated slurries and narrow particle size distribution.3.4 Chemical Modification Slurry sampling in ETAAS allows the use of chemical modifiers. The interaction between the chemical modifier and the particles of the solid sample is closer than for direct solid sampling. Most of the work on chemical modification for the slurry technique has been carried out in order to stabilize highly volatile elements such as Pb and Cd. 172,199.203-208 Karwowska and J ~ c ~ s o ~ ~ ~ ~ * ~ ~ ~ studied the release mecha- nism of Pb from alumina particles as a function of the location of analyte in the particles i.e. adsorbed or occluded. A mixture of (NH4)2HP04 and Mg(N03) was recommended as a chemical modifier and successful calibration with aqueous standards was reported.The assumption was made that in soil samples Pb is adsorbed onto the particles through covalent bonding with 0 and OH. However soil is a more complex matrix than aluminaJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 367 as it also contains organic material. MareEek and Synekfo9 studied the effect of the Ga occluded or adsorbed in alumina samples. The increase in peak height of the signal was attributed to the delay in the atomization caused by the alumina particles. Hinds and Jacksonzo5 used a mixture of montmorillonite and humic acid to simulate the behaviour of a soil matrix. A chemical modification study was carried out for Pb. Among the modifiers studied the best perform- ance was obtained with a mixture of magnesium and palladium nitrates.This chemical modifier leads to similar appearance times for the atomic absorption signal of slumes and aqueous standards. Palladium is efficiently reduced by the organic matter present in the Other procedures attempted for chemical modification in the determination of Pb in soil samples such as oxygen ashing pre-slurry ashing in a muflle furnace and the addition of nitric acid are less suitable as the peak characteristics differ significantly from those obtained with aqueous stan- d a r d ~ . ~ ~ ~ Hoenig and van Hoey~eghenl~~ used a mixture of (NH4)zHP04 Mg(N03)z and HN03 as chemical modifier for the determination of Pb and Cd in plant tissue sediment and lyophilized animal material; (NH4)zHP04 has also been used for the determination of Cd in olive leaves and mussels.zo3 For As Ni(N03)2178 and a mixture of Ni(N03)2 Mg(N03)z and HN03210 have been used; Ni(N03)z has also been used as a modifier for Se in selenized and in Ebdon and Parryz1 found that Ni(N03)z gave better performance than CU(NO~)~ or Pd(N03)2 as chemical modifiers for the determination of Se in coal.Graphite can be used for chemical modification in the slurry technique by adding fine graphite powder to the slurry. Carbon black has been used as a chemical modifier for the determination of Be and Mo in beryllium oxidezlz and molybdenum d i s ~ l p h i d e ~ ~ ~ respectively. The addition of carbon black prevented the interference of silica and caused a signal enhancement of about 3Ooh. Likewise this modifier enhanced A1 and Fe absorption signals by a factor of 1.5 when determined in aluminium oxide and iron oxide respectively.175 Graphite powder has been added to slurries consisting of non-radioactive simulated waste for the determination of Mo Ru Rh and Pd.214 Barnett et d Z l 5 used a mixture of Ca and Mg or Ni and Mg and La as chemical modifiers to determine boron a difficult element using the ETAAS technique in plant samples. Totally pyrolytic graphite tubes were used in order to minimize carbide formation. As for direct solid sampling the oxygen or air ashing technique facilitates pyrolysis of samples with high organic material contents and avoids any build-up of carbonaceous residues in the atomizer. 166*208~z1 lv2l6 The possibility of eliminating both the chemical modifier and the pyrolysis step in slurry sampling has also been studied.Those approaches require the use of isothermal conditions for atomization and Zeeman background correc- tion in order to avoid matrix interferences. Bradshaw and Slavinlg8 reported the rapid determination of As Pb T1 and Se in coal and coal fly ash matrices by automated ultrasonic agitation and elimination of the pyrolysis step. The preci- sion for replicates of slurries varied from 2 to looh depending upon the amount of solid sample delivered to the furnace. For the determination of As in fly ashls8 the background was lower when Pd was used as a modifier. However the background peak was separated from the As peak so that good precision was obtained. Bendicho and de L~os-Vollebregt'~~ have studied the influence of chemical modifiers such as magnesium nitrate palladium nitrate and a mixture of both in the atomization of Cu Co Cr Mn Ni and Fe in several glass materials. Studies by scanning electron microscopy demonstrated that the pyrolysis step caused an increase in particle size of the slurry sub-sample on the platform and therefore could be omitted.Chemical modifiers did not have any effect on recovery. Further research is required in order to establish the conditions in which rapid analysis can be carried out by avoiding the pyrolysis step and chemical modification without any deterioration in the analytical performance. 3.5 Calibration Calibration in slurry analysis can be accomplished by using the same approaches as mentioned for direct solids analy- sis. In contrast to direct solid sampling the slurry technique allows aqueous standards to be used for calibration in many instances.Quantification using aqueous standards has been carried out successfully in combination with different atomization conditions. Platform atomization and inte- grated absorbance quantificati~n,l~J~~ platform atomiza- tion and peak absorbance quantification wall atomiza- tion and integrated absorbance quantification181 and wall atomization and peak absorbance quantification2l7 have all been reported. Integrated absorbance measurements pro- vide accurate results even for wall atomization.181 The standard additions method or calibration using standard slurries were required for calibration when wall atomiza- tion was ~ s e d . ~ ~ ~ J ~ ~ Platform atomization does not always guarantee good accuracy when aqueous standards are used for calibration.The use of a chemical modifier is sometimes necessary in order to match the absorption signals produced by the analyte when in the aqueous standard and when in the slurry.205 The implementation of Zeeman background correc- tion,188 Smith-Hieftje background correctionz1 or wave- length facilitates slurry analysis because they allow effective correction for high background absorbances that arise from the atomization of the matrix. The use of STPF conditions as proposed by Slavin and co-w~rkers.~J~ has been recommended in order to eliminate spectral and chemical interferences. Recent work carried out with slurry sampling proved that the STPF conditions can also be successfully used for slurry atomization.z19 3.6 Applications of Slurry Sample Introduction The applications of slurry sample introduction in ETAAS are shown in Table 2.Applications are presented in a similar form as for direct solid sampling (Table l) the elements that are determined type of sample homogeniza- tion technique and relevant analytical results are also included. 4 Direct Solid Sampling Versus Slurry Sample Introduction The choice of one of the two approaches available for introduction of solid samples into electrothermal atomizers requires a critical look at the factors affecting the whole analytical procedure. The different factors to be considered are discussed below. 4.1 Sample Pretreatment Although it is evident that both direct solid introduction and slurry introduction can be successfully used for a variety of samples several criteria can be followed in order to indicate which procedure is preferable.For instance most applications reported for the analysis of pure metals alloys geological materials and plastics are based on direct introduction of the sample whereas for the materials that are originally in powder form such as sediments soils or particulate matter slurry introduction is preferred. From368 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1 99 1 VOL. 6 Table 2 Applications of slurry sample introduction in ETAAS Sample Element Na and Pb Alumina Ca Cr Cu Fe Pb Homogenization Magnetic Comments RSD=2-6% Reference 181 207 199 202 220 209 22 1 175 203 222 212 191 104 223 219 216 224 173 189 186 225 210 170 21 1 188 188 226 178 Magnetic Study of Pb atomization Study of Pb release from alumina RSD=2-5.4% Pb Magnetic K Na Mn Mg and Cr Ca Cr Cu Fe Na and Pb Ga Manual RSD=2-6% Alumina Ultrasonic and magnetic Suspension in ethanol- water (9+ 1).Wall and PT atomization. Peak height increases owing to the 'mini-platform' effect caused by the alumina Aluminium fluoride and Aluminium oxide and iron aluminium phosphate A1 oxide A1 and Fe Stabilization with high viscosity solvents RSD=4.3% for A1 and 2.4% for Fe Aquatic plants mussels and olive leaves Cd Pb NH4H2P04 as chemical Ascorbic acid as chemical modifier modifier Grinding and Ultrasonic agitation with zirconium spheres Beryllium oxide Be Carbon black as chemical modifier. RSD = 2.9% Biological and vegetal matter Pb and Cd Vortex mixing Carbonaceous slurry (digestion with sulphuric acid) Comparison of direct solid and slurry Comparison between digestion and slurry Single and multi-element determinations Use of an air-ashing step to reduce interferences PT atomization c u Pb Several Ultrasonic Biological matter - Ultrasonic probe Cr Co Pb and Mn Au and Ag Vortex mixing and Triton X- 100 Biological and organic matter Biological materials Biological and environmental samp.:s Chelating sorbents Coal 12 elements Mn Ultrasonic Multi-element determinations Rapid analysis.Automated slurry introduction Ultrasonic Ultrasonic Description of an ultrasonic slurry sampler Preconcentration of noble metals on sorbents Ni+Mg as chemical modifier. DL= 0.1 Au Pt Pd Ir and Rh Magnetic As Pug g-' 10% m/v slurrv DL=0.03 pg g-* for a As Se Magnetic + stabilizing agent Magnetic RSD= 5Oh; DL=*0.05 pg g-l for 15Oh m/v slurry.Air ashing in situ RSD=2-5%. Rapid analysis (1 min per sample) PT atomization and chemical modifiers. RSD = 3.3Oh As Pb T1 and Se Ultrasonic Be Automated mixing with magnetic stirring Ultrasonic +glycerol Coal fly ash As. Cd and PbJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 Table 2-continued 369 Sample Foods Foods tuffs Element Homogenization Comments Reference 208 184 200 227 177 194 202 228 229 230 23 1 180 168 63 232 213 214 Cd Pb O2 ashing in situ Pd as modifier. Freeze-dried sample. RSD = 4% O2 ashing and NH4H2PO4 as chemical modifier Batch sorption of elements from solution Rapid analysis. Study of chemical modifiers RSDs are improved by 1.5-2-fold with pre-digestion Carbonaceous slurry Resins are used as solid standards for hair analysis.Resins are used as solid standards DL,=0.6 pg g-' RSD= 8- 1 1 W Miniature magnetic agitation device Pb and Cd Stabilizing agent (Viscalex) Gels As Sb and Bi Magnetic Glasses Cu Co Cry Mn Fe and Ni Gas mixing Glasses Cu Coy Cry Mn Gas mixing and Fe and Ni pre-digestion of slurry with HF Several - Cu and A1 - Hashish Ion-exchange resin Hg Co Ni and Mo Magnetic Iron oxide Pb As Magnetic. Use of Triton X-100 and ammonium phosphate Magnetic Iron pigments Suspension in 0.1W m/v Triton X-100 and 0.1% m/v Ni. DL=0.2 pg g-' of As - Lubricating oil 10 elements Dilution with Zn Vortex mixing c u Water-ammonia- kerosene 1 ,4-dioxan as dispersion medium Cd Se Pb Zn - Cs Cu Cr and Mo Marine sediments Milk powder - Comparison between dry ashing wet digestion and slurry Comparison of direct solid sample (cup-in- tube) and slurry.RSD= 5-20°h (slurry) and 9-26% (solid sampling) black. RSD = 3-9% Addition of carbon Milk Molybdenum disulphide Mo Mo Ru Rh and Pd Ultrasonic - Non-radioactive simulated waste Comparison of direct solid sampling and slurry introduction. Samples are mixed with graphite RSD=4.3% Nutritional supplements Se Use of non-ionic surfactants for stabilization 174 Orchard leaves and Pine needles Plant matter pine needles Cd Cu Cry Fe and Pb Pb Mn Fey Cu Cr A1 and Mg RSD = 4Oh RSD=2-9% - Sources of contamination are identified and minimized (sample cups grinding reagents etc.) 190 218 167 233 - Ultrasonic Vortex mixing Automated ultrasonic mixing Plant and biological matter Mn T1 and Pb Vortex mixing and ultrasonic agitation Comparison of ETAAS and electrothermal atomization laser excited atomic fluorescence spectrometry 234 172 Plant tissue and sediments Stabilization with glycerol RSD=0.45-13Oh.DL=0.4 pg of Cd and 5 pg of Pb Pb and Cd370 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 Table 2-continued Element Homogenization Comments Reference Sample Plant tissue Cu Zn Fe and Mn B Magnetic Ultrasonic RSD=6% 217 Use of totally 215 pyrolytic tubes. Ni + Mg + La as modifier Pol ymer-supported River sediment catalysts Pd Stabilizing agent RSD= 0.07% 235 Pb Mn As and Fe Ultrasonic and Automated slurry 187 vortex mixing introduction.Study of error sources c u Use of a thixotropic - 169 thickening agent for stabilization Cd Cr Cu Ni Ultrasonic agitation - 236 Pb and Zn Rocks Sediments Sediments particulate matter Cu Cd Pb Co Stabilization with Cr and Ni glycerol. Pre-digestion of slurry Ultrasonic Al Ca Fe and Mg Cd Cr Cu Ni Pb and Zn Al Ca Fe and Mg - Pd modifier mixed 193 with matrix elements - 24 1 RSD = 8Oh 242 Sewage Sewage sludge RSD = 6- 1 1% for Al 243 1.7% for Ca 2.6% for Fe and 1.9Oh for Mg Wide range of sludge types 237 - 238 Comparison with 239 acid digestion and dry ashing acid digestion and dry ashing and colorimetric methods Comparison with 240 Comparison with FAAS 245 - Cd Cr Ni and Zn Ultrasonic Sb As Bi Te and Ultrasonic agitation T1 Ag Co Mn Mo and Ultrasonic agitation Sn Various - Sewage sludge and sewage efluent Pb Cu Cd Cr Ni and Zn Pb - 244 Stabilization with Stabilization with Magnetic Magnetic Viscalex (3Oh m/v) Viscalex (3% m/v) RSD = 3% 166 Spinach Pb DL=0.05 pg g-' 171 RSD=8% 182 RSD = 2-4Oh for Cd and 183 8-9Yo for Pb Study of chemical 204 components Study of chemical 205 modifiers 0.6 pg of Pd+ 1 pg of Mg 206 as chemical modifier Systematic study of 246 various Pd + Mg mixtures (Pd as nitrate and chloride). 0.6 pg Pd+ 1 pg Mg is optimum O2 ashing Pb Pb and Cd Soil Pb Magnetic Magnetic Pb Pb Magnetic Pb Steel alloys and pure metals Cu Fe Mg Mn Slurries prepared STPF conditions and 197 Pb and Zn with spark ablation calibration with aqueous standards Sulphate catalysts Fe Pt Stabilizing Tungsten strip agents heater for atomization Use of Triton X- 100 and stirring for 3-5 min - 247 179 Tissue samples Titanium ore and silicate rock Co Cr Cu and V Use of stabilizing Comparison between 198 agents flame plasma and electrothermal atomization Cu Fe Mn and Pb Sodium hexametaphosphate DL=O.l-0.5 pg g-I 248 is added to the slurry. Magnetic stirring and atomization Titanium oxideJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL.6 371 Table 2-continued Sample Element Homogenization Comments Reference Water Cd Cu Pb Coy Ni and Cd Cd c u Freeze-dried alga 249 is used for Cd preconcentration time required 4 min per sample with chelating sorbents (20-30 pm). RSD < 16.5% Cd preconcentration and analysed as slurry with an alga. Extraction of Cu is insensitive to pH algal mass and alkali and alkaline earth metals Metals preconcentrated 2 50 An alga is used for 25 1 Cu is preconcentrated 252 the point of view of sample pre-treatment some samples are more favourable for direct solid sampling owing to the difficulty of grinding e.g.metallic samples which are commonly analysed in the form of chips drillings or turnings. In addition slurries prepared from metallic particles are difficult to stabilize (unless spark ablation is used) or mix in order to yield a homogeneous suspension. Contamination risks exist when grinding materials such as rocks and refractories. Slurry preparation might be less useful for samples that are difficult to disperse and tend to float on the top of the liquid medium such as very light powders. 4.2 Sample Introduction Sample introduction is straightforward for slurries as conventional sample introduction systems in widespread use for liquid samples can be used without further modification.Sample introduction can be automated when using the autosampler; an advantage for routine determina- tions. Errors that can arise during the weighing and transfer operation in direct solid sampling are minimized in slurry sampling. Comparisons of direct solid sampling and slurry sample introduction indicate that although the same accuracy is reached precision is better when using the slurry technique. 4.3 Dilution of the Solid Sample Slurries can be diluted if required so that the absorbance falls into the analytically useful range of the calibration graph. When the analyte concentration is too high direct solid sampling requires dilution of the sample with graphite powder which can cause contamination or a change in the analytical conditions so that the sensitivity is decreased.Changing the analytical conditions i.e. the gas flow rate during atomization and the use of less sensitive lines requires additional optimization. 4.4 Sample Homogeneity For the slurry technique the representative sub-sample is based on the fraction of the total slurry volume that is actually introduced into the furnace. Extraction of the analyte into the slurry medium takes place when the slurry is prepared in acidic media and provides improved preci- sion for non-homogeneous samples. For direct solid sampl- ing the representative sub-sample is based on the amount of sample that is weighed and transferred into the atomizer.The influence of sample non-homogeneity on precision is similar for both direct solid sampling and slurry introduction. 4.5 Peakshape The dependence of the shape of the peak of the absorption signal on the solid matrix is more pronounced when the sample is atomized directly. Vaporization kinetics for the release of the analyte are usually slower when the particle size increases as reported for metallic chips or geological samples that were insufficiently ground. Peak shape for the volatile metals is similar using both approaches but broader peaks are usually obtained for the determination of refractory metals when using direct solid sampling; broad peaks are difficult to integrate in reasonable periods of time.4.6 Calibration Reliable results are usually obtained for direct solid sampling when samples of CRMs are available. In contrast calibration with aqueous standards constitutes a more realistic possibility in the slurry technique provided that appropriate analytical and instrumental methodology is used. 5 Conclusions Solid sampling in ETAAS has received great attention in recent years mainly because of the availability of commer- cial atomizers that facilitate sample introduction and satisfy the requirements for isothermal atomization. The most advantageous designs are probably those that use a graphite support (platform boat microboat and cup) for both sample weighing and atomization. However these systems are manually operated and therefore sample introduction requires training of the analyst. Although sample homogeneity is a critical factor influencing preci- sion it is not a determining factor in achieving accurate results.In many instances sample homogeneity can be improved by using a suitable grinding procedure. In addition sample homogeneity is not critical for many samples and therefore sample masses of about 1 mg can be successfully analysed. The slurry technique gives better analytical performance than direct solid sampling. The slurry concentration can be easily changed so that the analyte concentration falls into the analytically useful range of the calibration graph. More importantly slurry sample introduction can be easily automated. 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Paper I /004696 Received February Ist 1991 Accepted April I Oth 1991

ISSN:0267-9477    

DOI:10.1039/JA9910600353

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 375 Electrothermal Atomic Absorption Spectrometry of Inorganic and Organic Arsenic Species Using Conventional and Fast Furnace Programmes Erik H. Larsen National Food Agency of Denmark MQrkh#j 5ygade 19 DK-2860 Soborg Denmark Analytical sensitivities for arsenate monomethylarsonate dimethylarsinate arsenobetaine arsenocholine and the tetramethylarsonium ion are determined by electrothermal atomic absorption spectrometry. Conventional and fast furnace programmes with and without a palladium-magnesium nitrate chemical modifier are studied. Special attention is paid to pre-atomization losses of the arsenic species tested. The conventional programme gives equal characteristic masses of about 16 pg of arsenic for all the species tested.The characteristic mass is defined as that mass of analyte which produces an integrated absorbance signal whose net area is equal to 0.0044 A s. The fast programme with the chemical modifier leads to slightly poorer sensitivities compared with the conventional programme. When using the fast programme without chemical modification substantial pre- atomization losses of the quaternary arsonium compounds in particular are seen at a pre-treatment temperature of only 200 "C. Keywords Electrothermal atomic absorption spectrometry; inorganic and organic arsenic species; fast furnace programme; pre-a tomiza tion loss; chemical modification Arsenic species present in biological material have been separated by high-performance liquid chromatography (HPLC) and detected on-line by inductively coupled plasma optical emission spectrometry (ICP-OES)' and by inductively coupled plasma mass spectrometry (ICP-MS).* Continuous hydride generation atomic absorption spectro- metry (AAS) has also been used as an on-line method of detection,' but only arsenic species that form volatile hydrides can be measured in this manner.A new hyphe- nated on-line HPLC-atomic absorption spectrometric method4 overcame this problem by pyrolysis of the sepa- rated quaternary arsonium compounds followed by gas- phase thermochemical hydride generation. As previously described,s off-line detection of arsenic species after separation by HPLC may be performed by electrothermal AAS (ETAAS). Although detection of the separated arsenic species using on-line techniques is ideal ETAAS is still advantageous because of the sensitivity and ease of operation.Furthermore the instrumentation is available in many laboratories. The fairly long time required for the analysis of a series of collected fractions may be inconvenient for practical analytical work. There- fore fast graphite furnace programmes6 appear attractive in order to shorten the time needed for analysis. However quantitative detection of arsenic by ETAAS is prone to errors owing to pre-atomization losses.' In order to produce precise and accurate analytical data arsenic measurements should be performed without pre-atomization losses. It is therefore of interest to study the conditions under which ETAAS gives equal and optimum sensitivities for all of the arsenic species in question.The purpose of this paper is to present the analytical sensitivities obtained by ETAAS for aqueous standard solutions of arsenate (AsV ) monomethylarsonate (MMA) dimethylarsinate (DMA) arsenobetaine (AsB) arsenocho- line (AsC) and the tetramethylarsonium (TMAs) ion using conventional and fast furnace methods. Experimental Chemicals Standard solutions each containing 1000 pg g-l of hydro- gen arsenate disodium salt MMA disodium salt DMA sodium salt AsB or AsC bromide in water were provided by the Commission of the European Communities Com- munity Bureau of Reference Brussels (Belgium). Tetra- methylarsonium iodide was donated by Dr. J.-s. Blais (Macdonald College Quebec Canada). A standard solution of this compound was prepared by dissolution in water and the concentration was determined accurately by ICP-OES and ICP-MS.Working solutions containing 50 ng ml-l of arsenic were prepared from each of the six standard solutions. A chemical modifier solution was prepared by mixing equal volumes of a 3000 pg ml-1 solution of palladium and a 2000 pg ml-l solution of magnesium nitrate in water. Palladium powder (22 mesh 99.998% purity) was purchased from Alfa Products (Karlsruhe Germany). Palladium metal (300 mg) was mixed with 4.5 ml of 65Oh nitric acid and left overnight followed by sonication and step-wise addition of 1-2 ml of 37% hydrochloric acid until dissolution was complete and finally made up to 100 ml with water. Instrumentation and Methods A Perkin-Elmer 3030 Zeeman AAS instrument with an AS- 60 autosampler and HGA-600 graphite furnace was used for recording the absorbance signals.Pyrolytic graphite coated graphite tubes and platforms in tubes were used throughout. Argon (300 ml min-l) was used as the purge gas except during atomization (gas stop). Arsenic absorbance was monitored at the 193.7 nm line (bandpass 0.7 nm) with an arsenic electrodeless discharge lamp source (8.5 W). The four graphite furnace programmes tested and other instrumental variables are given in Table 1. Method 1 is in accordance with the stabilized temperature platform fur- nace (STPF) concept,* while methods 2 3 and 4 are so- called fast programmes6 with 27-32 s furnace times. Methods 1 and 2 include the palladium-magnesium nitrate chemical modifier while methods 3 and 4 do not.Results and Discussion Optimization of Fast Furnace Programmes In the fast graphite furnace programme described by Slavin ef aL6 a drying stage at 700 "C for 1 s was followed by a pre- treatment step at 400 "C. They commented that the dry temperature might be too high for specific applications. In the present study a maximum drying temperature of 300 "C was used and also a temperature ramping from ambient temperature to 300 "C for 5 s was necessary in order to prevent sputtering of the analyte solution. During the376 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 Table 1 Graphite furnace settings for methods 1-4 Method Parameter Dry1 Dry2 1 Temperature/"C 100 130 Ramp/s 5 10 Hold/s 20 50 2 Temperature/"C 300 400 Ramp/s 5 1 Hold/s 3 10 3 Temperature/"C 300 400 Ramp/s 5 1 Holds 3 10 4 Temperature/"C 200 200 Ramp/s 5 1 Holds 3 15 Pre- treatment 1100 20 30 20 1 4 20 1 4 20 1 4 Chemical Sample volume/ Atomization Clean modifier/pl Pl 2200 2650 10 20 0 1 4 3 0 3 0 3 0 3 2300 - 10 10 10 2300 - - 10 2300 - - I c E 2 6 1 A' /- \ E \ 'n 1 1 1 1 2 3 4 Method 14 Fig.1 Characteristic mass in pg of As per 0.0044 A s for six arsenic compounds determined by using four different graphite furnace methods. A AsB; B AsC C TMAs; D DMA; E AsV; and F MMA. See Table 1 for details. (Graphic presentation does not imply a functional relationship between the individual methods) development of the fast programmes a small mirror was positioned in the light path which allowed observation of whether sputtering of the analyte solution injected onto the platform occurred. Characteristic Mass for Methods 1-4 The results expressed as characteristic mass i.e.the mass of arsenic that gives an integrated absorbance reading of 0.0044 As are shown in Fig. 1. An increasing value indicates a poorer sensitivity. Method 1 gives characteristic mass values for all six species of between 15.9 and 16.8 pg of arsenic which is close to the value for arsenate reported by other worker^.^ The conventional STPF furnace programme which in- cludes the palladium-magnesium nitrate modifier is there- fore efficient in stabilizing both the inorganic and organic arsenic species tested. The reported characteristic mass values were calculated from measurements of approxi- mately 500 pg of arsenic except in method I where approximately 1000 pg were injected.On increasing the amount of arsenic in the range 500-2000 pg the character- istic mass increased slightly. This indicates that for all six compounds a completely linear relationship between absor- bance and amount of arsenic measured does not exist. Method 2 leads to almost identical characteristic mass values for AsV MMA and DMA compared with method 1 while values of 19 pg of arsenic per 0.0044 A s are obtained for AsB AsC and TMAs. In spite of the use of the chemical modifier small pre-atomization losses of these three com- pounds do occur. Results from methods 3 and 4 (no chemical modifier used) demonstrate significant and varying pre-atomization losses from one arsenic compound to another. Losses are smaller for method 4 than for method 3 owing to a lower temperature (200 "C) in the drying stages of method 4.Even then large losses of particularly the cationic arsenic species are observed. For the detection of arsenic species after separation by HPLC Brinckman et aLl0 used a fast graphite furnace programme with a 200 "C pre-treatment temperature but without chemical modification or a platform in the furnace. They found that the sensitivity (peak area) for DMA injected directly into the furnace was only about half of that for MMA and AsV. The results from the similar method (method 4 of the present study) show a much smaller loss of DMA compared with their findings. This may be attributed to the use of a platform in the furnace. Woolson ef al." also used a fast graphite furnace pro- gramme without chemical modification.After drying of the sample solution their method included a 1200 "C ashing step for 7 s. They found the same relative response (peak area) for AsV and MMA. However no absolute measure of sensitivity is given and the results indicate that losses occur when no chemical modifier is used in conjunction with the high pre-treatment temperature. Interferences The interferences caused by loss of arsenic during the heating cycle of the graphite furnace have already been discussed. When determining arsenic in fractions eluted from an HPLC column the possibility of spectral interfer- ence from the sample matrix and from the mobile phase of the chromatographic system used must also be considered. In measurements made using ETAAS non-specific absor- bance from matrix constituents is commonly corrected for by a continuum source (deuterium lamp) or by use of the Zeeman effect. In principle all co-injected elements or molecules that absorb light from the continuum source in a structured pattern within the spectral bandpass used can cause overcompensation.Phosphate has been reported as such an interferentI2 in the 0.7 nm spectral bandpass around the 193.7 nm arsenic line. The sample clean-up and the chromatography itself significantly reduces the com- plexity of the sample matrix and therefore also reduces the presence of interferents originating from the sample matrix. In ion-exchange HPLC of arsenic species phosphate buffers have been used as the mobile phase,13 and the possible interference from phosphate in ETAAS must be paidJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST special attention.However the phosphate interference is eliminated when using Zeeman-effect background correc- tion. l4 Conclusions In the present study equal sensitivities are obtained for the inorganic and all organic arsenic species by using the conventional STPF furnace programme. Therefore calibra- tion for all species is possible by standards prepared from only one calibrant e.g. arsenate. The conventional pro- gramme however is relatively slow in operation compared with the fast programmes which are about 2 min shorter in duration. The fast programme that includes the chemical modifier makes calibration of all species possible using two arsenic species as calibrants i.e. one for the quaternary arsonium compounds and one for the other species.The use of fast furnace programmes without chemical modification cannot be recommended because of substan- tial losses particularly of quaternary arsonium compounds. References 1 Morita M. and Shibata Y. Anal. Sci. 1987 3 575. 2 Shibata Y. and Morita M. Anal. Sci. 1989 5 107. 3 4 5 6 7 8 9 10 11 12 13 14 1991 VOL. 6 377 Haswell S. J. O’Neill P. and Bancroft K. C. C. Talanta 1985 32 69. Blais J.-S. Momplaisir G.-M. Marshall W. D. Anal. Chem. 1990,62 1161. Brinckman F. E. Blair W. R. Jewett K. L. and Iverson W. P. J. Chromatogr. Sci. 1977 15 493. Slavin W. Manning D. C. and Carnrick G. R. Spectrochirn. Acta Part B 1989 44 1237. Krivan V. and Arpadjan S. Frezenius Z. Anal. Chem. 1989 335 743. Slavin W. Manning D. C. and Carnrick G. R. At. Spectrosc. 1981 2 137. Schlemmer G. and Welz B. Spectrochim. Acta Part B 1986 41 1157. Brinckman F. E. Jewett K. L. Iverson W. P. Irgolic K. J. Ehrhardt K. C. and Stockton R. A. J. Chromatogr. 1980 191 31. Woolson E. A. and Aharonson N. J. Assoc. Ofi Anal. Chem. 1980 63 523. Saeed K. and Thomassen Y. Anal. Chirn. Acta 1981 130 281. Morita M. Uehiro T. and Fuwa K. Anal. Chem. 1981,53 1806. Fernandez F. and Giddings R. At. Spectrosc. 1982 3 61. Paper I /00195G Received January 15th 1991 Accepted February 2 7th I991

ISSN:0267-9477    

DOI:10.1039/JA9910600375

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 Comparison of Dry Mineralization and Microwave-oven Digestion for Determination of Arsenic in Mussel Products by Platform in Furnace Zeeman-effect Atomic Absorption Spectrometry N. Ybbiiez M. L. Cewera and R. Montoro 379 the lnstituto de Agroquimica y Tecnologia de Alimentos (CSIC) Jaime Roig 7 1 46070 Valencia Spain Miguel de la Guardia Depafiamento de Quimica Analitica Universidad de Valencia Or. Moliner 50 46 100 Burjassot Valencia Spain Two digestion procedures were compared in order to obtain an accurate method for the determination of As in mussel products using platform in furnace Zeeman-effect atomic absorption spectrometry. One procedure was based on dry mineralization of the samples and the other on microwave-oven sample digestion in closed polytetrafluoroethylene reactors.Microwave-oven digestion with HN03 and H202 allows the accurate determination of As in certified oyster and mussel tissue samples and provides results comparable to those found by dry mineralization of real mussel product samples with a sensitivity of 3.9 absorbance units per pg ml-’ and a relative standard deviation of 5% in the analysis of samples containing 8 pg g-‘ dry mass of As. Experimental conditions for the determination of As in real samples were optimized and a series of real samples analysed in order to determine the analytical characteristics of the proposed procedure. Sample treatment time was reduced from 2-3 d using dry mineralization to 20 min per sample using microwave-oven digestion. Keywords Arsenic determination; mussel product sample; dry mineralization; microwave-oven digestion; Zeeman-effect atomic absorption spectrometry The microwave decomposition technique seems to be the method currently preferred when preparing samples for the determination of the elemental composition of organic materials.At present marine biological samples are usually prepared by wet digestion with concentrated acids includ- ing perchloric acid or by dry mineralization with ashing as an aid prior to instrumental analysis using techniques such as flame and electrothermal atomic absorption spectrome- try (AAS). The use of HC104 can be dangerous in the presence of organic material and so the dry mineralization procedure is becoming more widely used because of its simplicity and safety.14 Nevertheless this sample treat- ment requires long heating periods which becomes the limiting factor determining the speed of analysis. Recently very fast safe and efficient acid decomposition methods based on the use of microwave ovens have been proposed for the determination of As in a variety of samples but few reports have been published on the determination of As in marine samples using microwave heating.Commercially available polytetrafluoroethylene (PTFE) pressure relief vessels or completely closed vessels have been used in microwave ovens with monitoring of the pressure during d i g e s t i ~ n . ~ ~ ~ The accuracy of the methodol- ogies has been tested by analysis of a National Research Council of Canada (NRCC) biological standard (lobster hepatopancreas TORT- 1 ).However until now there have been no publications in which real samples of marine foods have been analysed by electrothermal AAS following microwave-oven pressure digestion. It is evident that incomplete destruction of organic matter in the microwave oven could affect the accuracy of the analysis. The determination of As in marine biological samples by atomic absorption using the stabilized temperature plat- form furnace (STPF)’ concept in combination with Zee- man-effect background correction provides a dramatic reduction of non-spectral interference in fish tissues,* and the results are not affected by spectral interferen~e.~ In the present paper complete destruction of mussel products carried out by dry mineralization and acid extraction inside a microwave oven are compared as sample preparation methods for the platform in furnace Zeeman-effect atomic absorption spectrometric determina- tion of As.Experimental Equipment A Heraeus Model 1100/3 mume furnace equipped with a Jumo DPG-4411 digital microprocessor was used for mineralizing the samples. A domestic micro-wave oven Bauknecht Model MWT-732 programmable for time and microwave power in four discrete steps with eight power settings (ranging from 120 to 750 W) and a maximum time of 99 min 59 s was used without further modification. It is important to point out that different positions in the microwave cavity are not identical from the microwave irradiation point of view and so a prior study of the irradiation efficiency in each position is necessary. In order to carry out this study 35 Pyrex beakers (55 mm in diameter and with a volume of 250 ml) each containing 100 ml of distilled water were placed inside the cavity of the microwave oven covering the whole of the bottom surface of the oven.The oven was operated at maximum power for a total time of 2 h. After the beakers had cooled the loss of water from each beaker was measured and related to the level of microwave power absorbed taking the maximum loss of water as equivalent to a power absorption level of 1OOOh. Fig. 1 shows the microwave distribution in the oven from which it is concluded that the central position must be used in order to obtain effective sample decomposition. The polytetrafluoroethylene (PTFE) vessels used for the solutions were laboratory made and had a volume of approximately 120 ml with a 10 mm wall thickness and tight-fitting screw-cap lids.For pressurized acid digestion of the samples in thermal ovens hermetically sealed borosilicate glass tubes (40 ml) with Bakelite screw caps and Parr digesters with a volume of 55 ml were employed. A Perkin-Elmer Model Zee- man/3030 atomic absorption spectrometer equipped with an HGA-600 graphite furnace and an AS-60 autosampler was also used. This instrument includes a graphics display380 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 Fig. 1 Distribution of microwave radiation within the oven cavity unit and highly time-resolved signals were plotted with a Perkin-Elmer PR- 100 printer. Pyrolytic graphite coated graphite tubes with a L'vov platform inserted (Perkin- Elmer Part No.112660) were used exclusively. Reagents Analytical-reagent grade water with a metered resistivity of 18 MR cm was used to prepare all samples and standards. All reagents used were of the highest purity available and at least of analytical-reagent grade. An aqueous stock solution of As"' was prepared by dissolving arsenic(rI1) oxide. The ashing aid suspension was prepared by stirring 20 g of Mg(NOJ2-6H20 and 2 g of MgO in 100 ml of water until a homogeneous mixture was obtained. A nickel chemical modifier solution (0.1% m/v Ni) was prepared by dissolving the Ni(N03)2.6H20 in 1% v/v HN03. General Procedures Real and certified samples of mussel products were treated by both dry mineralization and microwave-oven decompo- sition and the digested solutions analysed by platform in furnace Zeeman-effect AAS.The experimental conditions of the microwave-oven digestion were optimized and a study of the atomization of samples and standards was carried out in order to obtain the best analytical character- istics and results from the two digestion procedures. 43.4 Samples Several cans of mussel products in brine and in pickled sauce were purchased at a local retail market. The brine or sauce was removed from the mussels by the method for determining drained mass in canned foods. The total contents of the can were emptied onto a sieve with a 5 mm stainless-steel mesh made of 1 mm gauge wire the sieve being tilted slightly to facilitate drainage. To ensure complete drainage the mussels were allowed to drain for 5 min.The drained mussels were then crushed and homogen- ized to a fine paste in a domestic Moulinex blender stored in previously de-contaminated glass flasks and kept in the freezer until the analysis could be carried out. A reference mussel product sample was prepared so that the different sample treatments could be compared. The paste obtained by crushing and homogenizing the mussels was dried at 100 k 3 "C to constant mass and then ground to pass through a 250 pm sieve and stored at -4 "C until required. Reference Samples Validation of the methods presented in this study was performed by using two reference materials one from the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1556a Oyster Tissue and the other from the Community Reference Bureau (BCR) Certified Reference Material (CRM) 278 Mussel Tissue. Results and Discussion Determination of Moisture in Mussel Products A microwave oven can also be employed as a drying system.Io Therefore in the present study the same appara- tus as was employed for sample digestion was used to determine moisture level.The results obtained using conventional drying in a thermal oven for 24 hours at 110 "C and those obtained in the microwave oven after 3 min at 385 W and 5 min at 555 W are summarized in Table 1. It can be seen that the differences between the two series of results are of the order of f 0.7%. Dry Mineralization The various experimental parameters for the mussel pro- ducts such as sample size amount of HN03 and ashing agents added mineralization steps in the muffle furnace and solubilization of the ash obtained were optimized.ll The different steps involved in dry mineralization of the mussel products are summarized in Table 2.The recom- mended procedure is as follows 5 ml of 5Ooh v/v HN03 and 1 ml of ashing aid suspension containing 20% m/v Mg(N03)2 and 2Oh m/v MgO were added to 0.250 g (dry mass) of mussel product or certified sample or 1.00 g (wet mass) of mussel product and the solution was mixed well. After evaporation to total dryness in a sand-bath the dry residue was subjected to a careful mineralization process (programme 1) in a muffle furnace at a temperature lower Table 1 Determination of moisture in mussel products Moisture content* (%) Sample Conventional Microwave E n o e (%I) 1 69.9 67.3 0.4 2 67.0 67.6 0.6 3 59.5 58.8 -0.7 * Average of three determinations.t The percentage ratio of the results obtained using a microwave oven and a thermal oven. Table 2 Steps involved in the dry mineralization of mussel products. The time taken to increase the temperature by 100 "C was 15 min and by 150 "C was 30 min Programme Step Temperature/"C Time/h I 1 150 1 2 200 0.5 3 250 1 4 300 3 5 350 0.5 6 450 12 I1 1 150 1 2 300 0.5 3 450 12JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 38 1 than 450 "C until a white ash was obtained. In general it was necessary to wet the ash with 50% v/v HN03 evaporate in a sand-bath and perform a second short mineralization process (programme 11) (once or twice) until the ash was completely white.The ash was dissolved with 2 ml of 50% v/v HN03 washed with water and filtered through What- man No. 1 filter-paper into a 50 ml flask. The solution was stored in a polyethylene bottle. Microwave-oven Digestion The dry mineralization procedure involves a very long (2 or 3 d) sample treatment time. To ensure complete dissolution of the marine samples for the determination of As by AAS the conventional sample preparation procedure is wet digestion. In order to release As from organoarsenic compounds mixtures of corrosive and sometimes explosive acids (including HClO,) and long heating periodsl1J2 or pressure decomposition9 are necessary. Moreover other workers have stated that it is necessary to maintain oxidizing conditions at all times particularly if chloride is present in order to prevent volatilization of As as the trichloride.The vital point seems to be that the sample must be heated in the presence of excess of nitric acid first and only allowed to char when the chloride has been removed as nitrosyl chloride.13 In order to avoid the dangerous use of HClO in the presence of organic material and to test whether the sample can be decomposed by acid digestion pressure decomposi- tion with nitric acid in a conventional oven was used initially since it has been reported that if a sample material cannot be decomposed by a conventional method prob- lems using the microwave heating technique will occur.14 Simple rapid pressure extraction with 0.5 ml of HN03 in a stoppered borosilicate glass container which was adequate for the determination of Cd Cu Fe Pb and Zn in mussels,15 provided unsatisfactory precision (1 4%) and low recoveries (95*39%) for the determination of As by platform in furnace AAS.For this reason acid digestion in a PTFE bomb heated to 140 "C for 1 h in a conventional oven with HN03 (1 2 or 5 ml) and HN03-HCl was tried prior to digestion in the microwave oven. The results obtained using 2 ml of acid are in agreement with the contents found in the reference mussel sample digested by dry mineralization. Finally the efficiency of the acid digestion procedure was enhanced by using a microwave oven. Different volumes of HN03 and H202 and different times and power settings of the microwave oven employing a single-stage or two-stage power and time setting were tested in order to ensure total recovery of As after sample treatment.Heating for 5 min at 555 W resulted in an excess of vapour pressure inside the vessel and sample charring. Therefore sample treatment was reduced to a two-stage power and time setting. The oven was operated at 555 W for 1 min and then the power was reduced to 300 W for 4 min. A 0.5 ml volume of HNOJ provided unsatisfactory recovery of As in the reference mussel sample similar to that obtained using 0.5 ml of HN03 in a stoppered borosilicate glass container. A 2 ml volume of HN03 digests 0.250 g (dry mass) of mussel sample yielding a solution with fat residues which gives promising results for the determination of As by platform in furnace AAS as indicated in Table 3.It is generally accepted that organic materials are not totally decomposed to C02 and water by HN03. Perchloric acid is used for the oxidation of resistant fat tissue and organoarsenic compound^.^ However using H202 avoids the use of HClO, eliminating difficulties associated with corrosive fumes and the potentially explosive nature of some nitric-perchloric acid mixture^.^ The addition of 2 ml of H202 with 2 ml of HN03 improves the efficiency of the digestion providing a clearer solution after sample diges- tion and greater accuracy in the analysis of real samples according to the results obtained by Matusiewicz et aL6 from an NRCC reference sample (lobster hepatopancreas The recommended procedure for microwave-oven diges- tion of samples was as follows 0.250 g of dry sample (mussel product or certified sample) or 1.00 g of wet sample (mussel product) was placed in a high pressure PTFE vessel and 2 ml of 65Oh m/v HN03 and 2 ml of 30% m/v H202 were added.The vessel was sealed with the screw cap and placed inside the microwave oven. Samples were irradiated at a 555 W power setting for 1 min and then the power was reduced to 300 W for 4 min. The vessel was removed from the oven and placed in a tray of ice-water for 15-20 min. The cap was removed the contents of the vessel washed with water and filtered through Whatman No. 1 filter-paper into a 50 ml flask and the solution was stored in a polyethylene bottle until required for analysis. TORT- 1 ). Table 3 Analytical characteristics of the methods Analytical procedure Microwave digestion Recovery of As Dry mineralization HN03 HN03-H202 Sensitivity/absorbance unit per pg ml-l Detection limit*/pg g-I Precision RSDt (4s) Mussel reference samplefl/pg g-' NIST SRM 1566a Oyster Tissuell/pg g-I (certified value 14.0 f 1.2/pg g-l) BCR CRM 278 Mussel TissueJI/pg g-' (certified value 5.9 f 0.2/pg g-l) 4.6 4.0 3.9 2.4 1.5 1.8 2 3% 69 5 8.3 +- 0.2 7.5 f 0.2 8.2 f0.3 13.1 k0.8 14.0k 0.6 13.1 & 1.2 6.0 k 0.2 - 6.2 f 0.3 * Eight reagent blanks were employed.$ Sample mass=0.250 g (dry mass). 9 Sample mass = 1 .OO g (wet mass). fl Mean and confidence semi-interval at the 95% confidence level based on analyses of eight replicate 0.250 g samples. 11 Mean and confidence semi-interval at the 95% confidence level based on analyses of four replicate 0.250 g samples.RSD = relative standard deviation from eight independent analyses.382 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 Table 4 Graphite furnace operating conditions for the determination of As in mussel products Operating conditions- Electrodeless discharge lamp Wavelength Spectral bandwidth Background correction Measuring mode Graphite furnace Furnace tube Injection mode Sample volume Chemical modifier 8.5 W 193.7 nm 0.7 nm (low) Zeeman Integrated absorbance calculated by HGA software Pyrolytic graphite coated graphite tubes with a L'vov platform Autosampler AS40 10 pl of Ni (0.1 Oh mlv) HGA-600 20 pl Furnace programme- Timels Internal Step "C Ramp Hold ml min-l Temperature1 Ar flow rate1 Drying Drying Mineralization Mineralization Atomization Cleaning Cooling 90 10 20 300 120 10 20 300 800 10 10 300 1100 10 10 300 2300 0 5 0 2650 1 5 300 20 10 10 300 Optimization of the Graphite Platform in Furnace Pro- gramme For the graphite platform in furnace Zeeman-effect atomic absorption spectrometric determination of As 1 ml of H20 and 20 pl of standard solutions containing 0 2 4 and 6 pg ml-l of As were added to digested sample aliquots of 1 ml and the resulting solutions were analysed using the standard additions method under the experimental condi- tions indicated in Table 4.The recommended analytical conditions for pyrolytic graphite coated platform in furnace Zeeman-effect determi- nation of As with STPF conditions16 are the addition of 10-20 pg of Ni (as nitrate) as a chemical modifier a thermal pre-treatment temperature of 1300 "C and an atomization temperature of 2300 "C.The atomization and mineraliza- tion temperature-time programme was optimized in order to provide maximum matrix decomposition without loss of As compatible with minimum background and maximum As absorbance in the atomization stage. Experimentally it has been confirmed using As standards that the Zeeman- effect signal increases between 1800 and 2300 "C thereafter decreasing. In order to enhance the lifetime of the graphite tube the atomization temperature for real samples can be decreased from 2300 to 2100 "C without any significant differences. Between 1000 and 1500 "C the mineralization temperature has no influence on the absorbance values obtained for an acidic standard solution of As and real samples.On the other hand a mineralization time of 10 s gives similar sample mineralization to a time of 60 s but the corresponding background signal is slightly increased. Matrix Effects In order to study the effect of the matrix on absorbance and background signals solutions were prepared containing 40 ng ml-l of As and various percentages of digested sample (0 10 25 50 75 and 100%). The matrix effect was evaluated in the presence of 10 and 20 pg of Ni as chemical modifier. Fig. 2 shows the results obtained. Significant differences were not detected between the use of 10 and 20 pg of Ni as chemical modifier. The variations in absorbance and background using solutions with 10 and 25% of digested 0.25 1 0 20 40 60 [AsVng mi-' Fig.3 Analytical curves obtained using the standard additions method A 0; B 25; C 50; D 75; and E 100% of the digested sample in the volume injected on the platformJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 383 0.4 0.3 9) C n U 5 0.2 9" 0.1 0 0 20 40 60 80 [AsYng ml-' Fig. 4 Calibration graphs obtained using A aqueous acid stan- dards and B the standard additions method for 10 pg of Ni added I A I -2 8 0 fG1-O s 11 ,... ....._ AA 0.5 I BG 1.0 I C 0 0 5 Timeis Fig. 5 Absorbance versus time profiles. for As determination @g g-I) in mussel products A dry mineralized mussel product; B HN03 microwave digested mussel product; and C HN03-H202 microwave digested mussel product. Solid lines correspond to absorbance readings and broken lines correspond to background readings slight increase in back ground.The influence of the matrix effect on the slope of the calibration graph was also studied. Fig. 3 shows the decrease in the slope of the standard additions graph when the percentage amount of digested sample in the solution injected on the platform increases and indicates that solutions with > 50% of digested sample strongly reduce the slope of the graph. In view of these results solutions with 50% of digested sample were selected to be injected onto the platform. In order to express the results in pg g-l from solutions containing a lower percentage of digested sample the instrumental readings must be multiplied by a very high factor (1 000 for 10% of digested sample and 800 for 25% of digested sample) which makes the analytical character- istics detection limit precision and accuracy unacceptable.The solution containing 50% of digested sample allows the determination of the As content of the spiked sample in the concentration range between the detection limit and 11.6 pg g-l for the microwave digested sample working within the linear range up to 0.900 absorbance units. The matrix effect was also observed in dry mineralized samples as can be seen in Fig. 4. It was verified that the effect is not due to the use of Mg as an ashing aid by comparing calibration graphs for As without Mg and those containing Mg in amounts 5 and 10 times higher than are present in dry mineralization (0 3 1 and 62 pg of Mg). The slopes of the calibration graphs show no significant differ- ences (3.26 3.48 and 3.24 absorbance units per pg ml-').A 50% solution of the ashed sample was selected to be injected onto the platform because the linear working range for analysis between the detection limit and 12.8 pg g-l (dry mass) was similar to that employed in microwave diges- tion. Moreover maintaining the same dilution factor in both methodologies allows a more accurate comparison of them. Non-spectral interference in the determination of As in mussel products caused by sample matrix cannot be totally corrected for in spite of the use of a Ni chemical modifier and STPF conditions and the standard additions method should be employed. Fig. 5 indicates the shape and size of the atomic absorption peaks for As and the corresponding background values when A dry mineralization; €3 microwave digestion with HN03; and C microwave digestion with HN03-H202 were used.The use of magnesium salts in dry mineraliza- tion increases the background signal. A typical background value for the aqueous As standards and HN03 microwave digests is of the order of 0.075 A and for HN03-H202 microwave digests 0.122 A. However atomization of dry mineralized samples gives background values of 0.190 A. Comparison of Analytical Characteristics of the Method In order to check the validity of the proposed methods for the determination of As in mussel products the analytical characteristics such as sensitivity detection limit precision and accuracy were evaluated in accordance with IUPAC recommendations. Sensitivity was established from the mean value of the slopes of the standard additions curves and expressed in absorbance units per pg ml-l.The detection limit established as the As concentration in pg g-l (dry mass) of mussel product which provides an absorbance reading statistically different from that of the blank was calculated by dividing three times the standard deviation of the absorbance readings of the reagent blanks (which were always of a very low magnitude) by the sensitivity taking into account the sample mass and dilution employed. Precision is expressed as the relative standard deviation (RSD) of eight independent analyses of the same sample of mussel product (reference sample). In order to evaluate the accuracy of the methods two certified samples SRM 1566a Oyster Tissue and CRM 278 Mussel Tissue were analysed. The results are given in Table 3 and demonstrate that both the proposed methods dry mineralization and HN03-H202 microwave digestion are appropriate for the determination of As in real samples.The higher matrix effect in the microwave digests slightly decreases the analytical sensitivity. The detection limits obtained by the three methods (including HN03 microwave digestion) are comparable because as the concentrations of As in the reagent blanks are almost indetectable in all instances their reproducibil- ity mainly depends on instrumental noise. The three detection limits are adequate for the determination of As in the mussel products analysed. The precisions found for the three digestion methods are comparable.The greater efficiency of HN03-H202 com- pared with HN03 digestion of the mussel reference sample in the microwave oven does not provide greater analytical precision. On the other hand the precision is slightly less when a wet mussel product sample instead of the dried sieved reference mussel product sample is analysed. The high level of accuracy of the methods is demon- strated by the good agreement of the results obtained in the analysis of the reference materials with the certified results.384 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 Table 5 Analysis of real samples Concentration of Aslpg g-* Sample Dry mineralization A B C D E Averagelpg g-' Standard deviationlpg g-I RSD (%) xk c10.05*/pg g-1 5.4 f 0.2 6.9 k 0.4 8.8 f0.5 6.1 f 0.3 6.0 f 0.6 6.6 1.3 20 6.6 +- 1.6 * X+ - CI0.05 = mean f confidence semi-interval at the 95% confidence level.Microwave digestion 7.2 f 1 .O 5.9 f 0.8 9.3 k 0.8 5.5 ? 0.3 6.3 f 0.3 6.8 1.1 22 6-82 1.9 Nevertheless the microwave-oven digestion with HN03-H202 provides the most accurate results for the analysis of Oyster Tissue. In the analysis of the reference mussel product sample by microwave digestion the additional use of H202 gives higher As contents than that obtained employing only nitric acid and this is in good agreement with the data obtained by dry mineralization. Analysis of Real Samples The determination of As in real mussel product samples was carried out by dry mineralization and microwave-oven digestion procedures. The results obtained in three replicate analyses of five real samples by the two methods used are comparable as can be seen in Table 5 Applying a Student's t-test to the mean concentrations obtained by the two methods the experimental t value obtained falls within the acceptance area of the null hypothesis at a significance level of a=0.05 (te,,=0.24<t8=2.306).Table 5 also shows that the confidence limits for the mean concentrations obtained by the two methods almost completely coincide. Conclusions Mussel product digestion with HN03-H202 in a pressur- ized PTFE vessel using microwave heating for a graphite platform in furnace AAS determination of As provides an efficient alternative to conventional dry mineralization. The detection limit precision and accuracy are similar for the two methodologies and appropriate for the determina- tion of As in real samples.Sample preparation times are reduced from 2-3 d using dry mineralization to about 20 min including subsequent cooling time employing the microwave heating source. Funds to carry out this work were provided by the Comisi6n Interministerial de Ciencia y Tecnologia (CI- CyT) Projects ALI89-052 1 and PB88-035 1 for which we are deeply indebted. References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Sturgeon R. E. Willie S. N. and Berman S. S. J. Anal. At. Spectrom. 1986 1 11 5 . Dabeka R. W. and Lacroix G. M. A. J. Assoc. Off Anal. Chem. 1987,70 866. Krynitsky A. J. Anal. Chem. 1987 59 1884. Brumbaugh W. G. and Walther M. J. J. Assoc. Off Anal. Chem. 1989,72,484. Nakashima S. Sturgeon R. E. Willie S. N. and Berman S. S. Analyst 1988 113 159. Matusiewicz H. Sturgeon R. E. and Berman S. S. J. Anal. At. Spectrom. 1989 4 323. Slavin W. Manning D. C. and Carnrick G. R. At. Spectrosc. 1981 2 137. May T. W. and Brumbaugh W. G. Anal. Chem. 1982 54 1032. Welz B. and Schlemmer G. J. Anal. At. Spectrom. 1986 1 119. de la Guardia M. Empleo de 10s Hornos Microondas en Quimica Universidad de Valencia 1990. Agemian H. and Thomson R. Analyst 1980 105 902. Maher W. A. Talanta 1983 30 534. Gorsuch T. T. The Destruction of Organic Matter eds. Belcher R. and Frieser H. Pergamon Press 1st edn. vol. 39 1970. Ohls K. ICPZnJ Newsl. 1990 15 784. Solchaga M. Montoro R. and de La Guardia M. J. Assoc. Ofl Anal. Chem. 1986,69 874. Perkin-Elmer Analytical Methods for-Furnace Atomic Absorp- tion Spectrometry Perkin-Elmer Uberlingen Publication B332 1984. Irving H. M. N. H. Freiser H. and West T. S. International Union of Pure and Applied Chemistry Compendium of Analytical Nomenclature Pergamon Press Oxford 1978. Paper Om485 5 K Received October 29th I990 Accepted February 8th 1991

ISSN:0267-9477    

DOI:10.1039/JA9910600379

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 385 Determination of Tributyltin and Inorganic Tin in Sea-water by Solvent Extraction and Hydride Generation Electrothermal Atomic Absorption Spectrometry Ni Zhe-ming Hang Heng-bin Li Ang He Bin and Xu Fu-zheng Research Centre for Eco-Environmental Sciences Academia Sinica P. 0. Box 934 Beijing China An ultrasensitive method for the determination of tributyltin and inorganic tin has been developed by in situ concentration of tin hydrides on a zirconium coated graphite tube with subsequent detection by electrothermal atomic absorption spectrometry (ETAAS). Characteristic mass values of 20 and 14 pg were obtained for tributyltin and inorganic tin respectively where characteristic mass is defined as that mass of analyte which provides a defined peak absorbance of 0.0044 A.The relative standard deviations for ten replicate measurements were 5.6% for tributyltin and 3.4% for inorganic tin. For speciation studies tributyltin was extracted in dichloromethane and determined by ETAAS. The sensitivity of tin in organic solution was about the same as that for inorganic tin in aqueous solution. The method proposed was applied to the analysis of water and satisfactory results were obtained. Keywords Electrothermal atomic absorption spectrometry with in situ Concentration; solvent extraction; zirconium coated graphite tube; stannane and tributyltin hydride generation; sea-water The occurrence of organotin compounds in the environ- ment and their impact on the biota have urged the need for the development of sensitive rapid and reliable analytical methods for their determination.The chemistry of tin from an analytical viewpoint has been comprehensively re- viewed.'q2 A variety of techniques have been proposed for the determination of alkyltin species in environmental samples including extraction of tributyltin followed by electrothermal atomic absorption spectrometry (ETAAS),3-6 hydride generation followed by cryogenic trapping and atomic absorption detection using a quartz cuvette at~mizer,~-l coupling of gas chromatographic or liquid chromatographic separation with electron capture,'* flame photometric,13 mass spectr~metricl~ or atomic ab- sorption spectrometric detectors. 15-17 This paper describes a sensitive and rapid method for the determination of tributyltin and inorganic tin in sea-water by solvent extraction and in situ concentration of the tin hydrides on a zirconium coated graphite tube with subsequent atomiza- tion and detection by AAS.The present method has the advantage of avoiding multiple manipulations which might introduce contamination or lead to loss of the analyte. Characteristic mass values of 20 and 14 pg were obtained for tributyltin and inorganic tin respectively where charac- teristic mass is defined as that mass of analyte which provides a defined peak absorbance of 0.0044 A. Experimental Apparatus All the experiments were carried out on a Perkin-Elmer 4000 atomic absorption spectrometer with a deuterium arc background corrector and equipped with an HGA-400 graphite furnace.The operating parameters for direct injection were wavelength 224.4 nm; dry at 100 "C (40 s); char at 500 "C (30 s); and atomize at 2400 "C (4 s). The gas flow was interrupted during atomization and the maximum power heating mode was used. Peak height measurements were used throughout. A laboratory-built hydride generator HG- 100 (Research Centre for Eco-Environmental Sciences Beijing China) was used; the construction and function are similar to those described previously. Hydride generation was accom- plished by using two channels of a peristaltic pump to deliver the sample solution and potassium tetrahydroborate solution. The liberated hydrides were stripped from the solution by the argon gas and were introduced onto the zirconium coated graphite tube via the tip of a quartz tube. When the adsorption of the tin hydrides was complete the quartz tube was removed from the furnace and the tin absorbance was recorded at the atomization temperature of 2400 "C.Insertion of the quartz tube into the graphite tube and its removal were performed automatically. A high intensity tin lamp (General Research Institute of Non-Ferrous Metals Beijing China) was used as the line source. Pyrolytic graphite coated graphite tubes (Union Spectroscopic Technology Investment Beijing China) were used. Coating of the tube surface was achieved by soaking the tube overnight in a solution of 5% ZrOC12-8H20. The coated tube was dried at about 200 "C for 3-4 h. The tube was again treated in the furnace by injection of 100 pi of a zirconium solution onto it with subsequent drying at 100 "C and surface activation at 2000 "C.The treatment was repeated five times. The tube had a lifetime of 150-200 firings. Reagents A stock solution of tin 1 pg ml-' was prepared by dissolving 0.100 g of tin metal powder (99.999%) in 30 ml of 12 mol dm-3 hydrochloric acid and diluting to 100 ml with 5% citric acid in de-ionized water. The stock solution was diluted with 5Oh citric acid in 3 mol dm-3 hydrochloric acid to a concentration of 10 pg ml-' of tin. The final standard solutions were obtained by diluting the above solution with 0.01 mol dm-3 hydrochloric acid to the ng ml-l concentration range. These solutions were prepared just prior to use. Bis(tributy1tin) oxide (Beijing Chemical Industries Beijing China) containing 0.100 g of tin was dissolved in 50 ml of ethanol and diluted with 3 mol dm-' hydrochloric acid containing 5% citric acid to 100 ml to obtain 1 mg ml-l of tin.The organotin solutions were diluted to 10 pg ml-' with 5% citric acid in 3 mol dm-3 hydrochloric acid. The final standard solutions in ng ml-l concentration ranges were prepared just prior to use. Potassium tetrahydroborate solution (4% m/v) was pre- pared daily by dissolving KBH4 (Shanghai Chemical Reagent Factory Shanghai China) in de-ionized water and was used without filtration and without the use of a stabilizing agent. All chemicals were of analytical-reagent grade.386 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 Procedure Hydride generation ETAAS The furnace programme and procedures for hydride genera- tion collection and atomization are briefly listed in Table l.The sequence of operations was as follows. After the initiation of the programme the tip of the quartz tube from the outlet of the hydride generator was inserted through the sample introduction port at the centre of the zirconium coated graphite tube and held in contact with the opposite interior wall. The furnace was heated to 500 "C and the peristaltic pump was then started. The samples in 0.01 mol dm-3 hydrochloric acid and 4% KBH4 solutions were delivered to the generator at a rate of 3 ml min-l for 20 s. The generated hydrides were swept with argon and hydro- gen into the furnace and adsorbed onto the zirconium coated graphite tube. The argon flow rate was 0.3 1 min'l.A period of 100 s was used to collect the tin hydrides at a temperature of 500 "C. The quartz tube was then automati- cally removed from the introduction port of the graphite tube and the atomic absorbance was measured at 2400 "C. Solvent extraction-E TAAS A 10-20 ml volume of diluted sea-water (1 + 1) containing tin compounds was transferred into a 125 ml glass separat- ing funnel. The solution contained 0.001 mol dm-3 hydro- chloric acid. A 1.0 ml volume of 4% m/v NaBH solution and 1 .O ml of dichloromethane were added. The funnel was capped with a glass stopper and shaken by hand for 1 min vented and then shaken for 5 min. After a 10 min settling period the lower organic layer was removed into a microsampling cup with a cap. A 10 p1 volume of the organic solution was injected into the zirconium coated graphite tube using a microsyringe and the absorbance of tin was measured.Results and Discussion Trapping of Tin Hydrides on the Zirconium Coated Graphite Tube The use of a palladium coated graphite tube greatly improved the trapping efficiency of metallic hydrides as compared with the uncoated graphite tube.18J9 The sensi- tivities for the determination of arsenic selenium tellu- rium bismuth antimony and germanium by hydride generation combined with ETAAS were sufficiently high for the analysis of natural water and sea-water. In situ concen- tration of stannane in a graphite furnace has been re- ported.20 The efficiency of generation trapping and atomi- zation for tributyltin relative to inorganic tin hydrides was 46%.The addition of palladium to the furnace produced the same efficiency for the trapping of stannane.20 Our experi- ments showed that in comparison with the standard graphite tube both palladium and zirconium coated graph- ite tubes were found to be 2-4 times more efficient for trapping the hydride derivatives of inorganic tin and organotin. However the zirconium coated graphite tube was preferred because the zirconium remained on the Table 1 Furnace programme Temperature/ Ramp/ Hold/ Step "C S S Procedure - 1 100 5 2 2 500 5 5 Insert quartz tube 100 Hydride generation and collection 8 Remove quartz tube 3 2400 0 4 Atomization graphite tube and the enhanced trapping effect for tin lasted for more than 100 firings. The calibration graphs for stannane and tributyltin are linear over the concentration range 0-2.0 ng ml-l of tin and the sensitivity of tributyltin is only 7Ooh relative to that of stannane.A probable reason for the result was the lower volatility of the tributyltin hydride (b.p. 280 "C) as compared with stannane (b.p. - 52 "C). Characteristic mass values obtained using peak height measurement of 14 and 20 pg were obtained for inorganic tin and tributyltin respectively which is better than that reported previously.20 The relative standard deviations for ten replicate measurements were 3.4Oh for inorganic tin and 5.6Oh for tributyltin. The detection limits for inorganic tin and tributyltin were 58 and 78 pg respectively. The reagent blank was found to contain 0.340 2 0.003 ng of tin. Optimization of Signal The conversion of tin into stannane prior to determination by AAS has been well d~cumented.~g*~-~~ Studies on the conditions required for optimization of the signal such as NaBH concentration and pH value for the generation of tin hydride have shown that the highest absorbance resulted from acidification of the sample solution to pH 2 followed by the addition of 1.5 ml of 4% NaBH s~lution.~ Our experimental work confirmed the above results.There- fore a sample solution containing 0.01 mol dm-3 hydro- chloric acid and 1.0 ml of 4% KBH4 which gave stable absorption signals for the hydrides of both inorganic tin and organotin was used. The dependence of the recovery of tin on the sorption temperature of the furnace is shown in Fig. 1. As can be seen the recoveries of stannane increased on raising the temperature from 100 to 400 "C and then levelled off between 400 and 600 "C while that of tributyltin was nearly constant over the temperature range of 100-700 "C.The optimum response as a compromise for both inorganic tin and organotin can be obtained at 500 "C which was used for further studies. The stripping of the hydrides of tin out of solution increased with purge time using argon at a flow rate of 0.3 1 min-l. As shown in Fig. 2 a period of 80-90 s was- required for the complete recovery of the tin compounds examined. Separation and Determination of Tributyltin Since the contribution of tributyltin hydride to the absorp- tion signal was lower than that of inorganic tin hydride generation ETAAS was not adequate for total tin determi- nation. For quantitative measurements of tributyltin a separation procedure using solvent extraction should be carried out.The inorganic tin concentration can be calcu- lated by subtraction of the absorbance due to tributyltin from the total absorbance obtained by hydride generation ETAAS. I 1 I I 1 300 500 700 Temperature/"C Fig. 1 Dependence of tin recovery on the sorption temperature of the furnace 1 ng of Sn in A stannane; and B tributyltinJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 387 ~~~~~~~ ~ Table 2 Analysis of sea-water Sea-water Sn sample addedhg ml-' 1 1 .o 2.0 5.0 2 6.0 5.0 2.0 * Mean of three determinations. Sn added as tributyltidng ml-1 1 .o 0.50 1 .o 3.0 4.0 6.0 Sn found*/ng ml-I 0.94 2.2 5.2 5.5 5.4 1.8 Sn found as tributyltidng ml-1 1.2 0.59 1 .o 3.3 3.6 6.0 I * 30 50 70 90 Time/s Fig.2 Effect of sorption time on recovery of tin 1 ng of Sn in A stannane; and B tributyltin Tributyltin in sea-water has been extracted by using toluene.6 However this procedure when applied to fresh- water samples was hindered by emulsification of the toluene in the aqueous layer. Recoveries were poor and strong interferences occurred in the graphite furnace. In order to reduce the emulsified layer sodium chloride and methanol should be added. Butyltin hydrides have been extracted by using dichloromethane followed by gas chro- matography-flame photometric detection.25 It was found that the tributyltin hydrides in dichloromethane can be directly determined by ETAAS. The organic layer was easily separated from the aqueous layer and remained clear after shaking for 5 min.The dependence of absorbance on concentration of tin is found to be similar for tributyltin in dichloromethane and inorganic tin in aqueous solution giving a linear calibration with absorbance increasing from 0 to 0.20 for 0-6.0 ng of tin. Since inorganic tin was not extracted into the organic layer the method provided a useful procedure for the separation of tributyltin from inorganic tin prior to its determination. Analysis of Sea-water The sea-water samples received which had previously been filtered contained no measurable levels of tin compounds. In order to test the applicability of the proposed method mixtures of varying proportions of inorganic tin and tributyltin were added to the sea-water samples and the concentrations were determined using the procedures de- scribed.The results shown in Table 2 indicate that recoveries of inorganic tin and tributyltin are 90-1 10 and 90- 120% respectively. The suppression effect of the matrix on tin hydride generation can be minimized by diluting the sea-water. Conclusion In situ concentration of inorganic and tributyltin hydrides onto a zirconium coated graphite tube with subsequent detection by ETAAS provided a sensitive and rapid method for their determination. The method can be applied to other hydride forming elements such as lead and to volatile organometallic compounds. This work was supported by the National Natural Science Foundation of China under Grant No. 2870321. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 References Weber G.Fresenius Z. Anal. Chem. 1985 321 217. Thompson J. A. J. Sheffer M. G. Pierce R. C. Cooney J. J. and Maguire R. J. Organotin Compounds in the Aquatic Environment NRCCKNRC 22494 Ottawa Canada 1985. Chamsaz M. and Winefordner J. D. J. Anal. At. Spectrom. 1988 3 119. Sullivan J. J. Torkelson J. D. Wekell M. M. Hollingworth T. A. Saxton W. L. Miller G. A. Panaro K. W. and Uhler A D. Anal. Chem. 1988 60 626. Stephenson M. D. and Smith D. R. Anal. Chem. 1988 60 696. Donaghy C. Harriott M. and Thorburn Bums D. Anal. Proc. 1989 26 260. Donard 0. F. X. Rapsomanikis S. and Weber J. H. Anal. Chem. 1986 58 772. Chau Y. K. Wong P. T. S. and Benqart G. A. Anal Chem. 1982 54 246. Randall L. Donard 0. F. X.and Weber J. H. Anal. Chim. Acta 1986 184 197. Balls P. W. Anal. Chim. Acta 1987 197 309. Hodge V. F. Seidel S. L. and Goldberg E. D. Anal. Chem. 1979,51 1256. Sodcquist C. J. and Crosby D. G. Anal. Chem. 1978 50 1435. Muller M. D. Anal. Chem. 1987 59 617. Meinema H. A. Burger-Wiersma T. Versluis-de Haan G. and Geners E. Ch. Environ. Sci. Technol. 1978 12 288. Ebdon L. Hill S. J. and Jones P. Analyst 1985 110 515. Brinkman F. E. Blair W. R. Jewett K. L. and Iverson W. P. J Chromatogr. Sci. 1977 15 493. Jewett K. J. and Brinkman F. E. J. Chromatogr. Sci. 1981 19 583. Zhango L. Ni Z.-m. and Shan X.-q. Spectrochim. Acta Part B 1989,44 339. Sturgeon R. E. Willie S. N. Sproule G. I. Robinson P. T. and Berman S. S. Spectrochim. Acta Part B 1989 44 667. Sturgeon R. E. Willie S. N. and Berman S. S. Anal. Chem. 1987 59 2441. Subramanian K. S. and Sastri V. S. Talanta 1980,27 469. De Doncker K. Dumarey R. Dams R. and Hoste J. Anal. Chim. Acta 1986 187 163. Andreae M. O. and Byrd J. T. Anal. Chim. Acta 1984,156 147. Evans W. H. Jackson F. J. and Dellar D. Analyst 1979 104 16. Matthias C. L. Olson G. J. Brinkman F. E. and Bellama J. M. Environ. Sci. Technol. 1986 20 609. Paper 0/02866E Received June 26th 1990 Accepted March 7th 1991

ISSN:0267-9477    

DOI:10.1039/JA9910600385

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 389 Hydride Generation Atomic Absorption Spectrometry From Alkaline Solutions Determination of Selenium in Copper and Nickel Materials* Torild Wickstrom and Walter Lund University of Oslo Department of Chemistry P.O. Box 1033 Oslo 3 Norway Ragnar Bye University of Oslo Department of Pharmacy P.O. Box 1068 Oslo 3 Norway Selenium is determined in copper and nickel materials without any interferences. Hydrochloric acid plus hydrogen peroxide are used to dissolve the samples. The solution is then made alkaline with sodium hydroxide in order to eliminate the interference from copper and nickel by precipitation of the corresponding hydroxides. Sodium tetrahydroborate is added to the alkaline solution in order to reduce selenium(iv) to the selenide ion and the solution is then filtered.The volatile selenium hydride is generated by acidification of the alkaline solution in a continuous flow system. The method was used successfully for the determination of selenium in three standard reference materials (SRMs) from the National Institute of Standards and Technology SRM 398 Unalloyed Copper V SRM 671 Nickel Oxide 1 and SRM 875 Cupro-Nickel 10 (CDA 706) (doped). The detection limit of the method was approximately 1 pg g-l. Keywords Hydride generation atomic absorption spectrometry; selenium in copper and nickel materials; removal of interfering metals as hydroxides Hydride generation atomic absorption spectrometry (HGAAS) has become an established technique for the determination of a range of elements.Arsenic antimony and selenium are probably the elements most frequently determined by this technique but there are many reports on the successful determination of bismuth germanium tin lead and tellurium. The generation of the volatile hydrides is normally carried out under strongly acidic conditions ( 1 - 10 mol dm-3) with sodium tetrahydroborate as the reducing agent. The acidic conditions are necessary in order to achieve both the effective formation and release of the hydride gases from the solution as the hydrides possess acid-base properties illustrated by the following equations for selenium hydride H2O H2Sek) * H2Se(aq) H2Se(aq)+H,0 =H,O++HSe- Ka,=1.3x HSe-+H,O *H30++Se2- Ka2=1.0x lo-" In a strongly acidic solution the dissociation of H2Se is suppressed.Normally the sample solution is acidified prior to the hydride generation as part of the sample preparation procedure but this might not always be advantageous. For example (z) if the chloride concentration of a sample is high (e.g. sea-water) the addition of acid can result in the reduction of selenium(v1) to selenium(Iv) thus losing the possibility of determining both species; (ii) if the sample is alkaline and contains the hydride-forming element in its lowest oxidation state (selenides and arsenides) the ele- ment may be lost as the volatile hydride upon acidification; and (iiz] it might be necessary to make an acidic sample solution alkaline in order to remove some interfering elements. Hence in all of these instances the reduction of the hydride-forming elements directly in neutral or alkaline solution would be advantageous.The principles of hydride generation from alkaline solutions have recently been described.' The method is based on the fact that the tetrahydroborate ion is a strong reductant in alkaline solution H2B03-+5H20+8e-+BH,-+80H- Eo= - 1.24V * Presented in part at the Fifth Biennial National Atomic Spectroscopy Symposium (BNASS) Loughborough UK 18th-20th July 1990. Tetrahydroborate is therefore capable of reducing the hydride-forming elements in alkaline solutions not to the gaseous hydride but to the corresponding anion e.g. for selenium 4Se032- + 3BH4- + 4Se2- + 3H2B03- + 3H20 This can be utilized by adding sodium tetrahydroborate directly to an alkaline sample solution. After reduction of a given element to the corresponding anion acid is added in order to form and release the gaseous hydride.The addition of acid is most conveniently carried out using a continuous flow generator but a batch technique can also be used. The serious interference from copper and nickel and other metal ions in the determination of selenium by the HGAAS technique has been well do~umented.~~~ Several approaches for minimizing such interferences have been suggested including the addition of various reagents such as thiourea4 and iron(1n) soluti~n.~-~ Interfering metals can also be removed by precipitation. Thus Welz and Melche? removed nickel by precipitation as nickel hydroxide. The procedure involved filtration before the solution was acidified diluted to volume and analysed in the conven- tional way.The procedure for removing interfering metals by precip- itation as the hydroxides is simplified by carrying out the reduction directly in an alkaline solution because the number of steps is then reduced. In this paper such a method is described for the determination of selenium in copper and nickel materials as an example of the usefulness of hydride generation from an alkaline solution. Experimental Apparatus and Operating Conditions A Perkin-Elmer Model 300 atomic absorption spectrometer and an Omniscribe (Houston Instruments Austin TX USA) Model D-5 1 16-2 recorder were used. The electrode- less discharge selenium lamp was operated at 196.0 nm. A continuous flow hydride generator (P.S. Analytical Seve- noaks Kent UK) was operated with the following settings delay 15s; measure 30s; and reset 20s.The gas-liquid separator of the hydride generator was connected to a 19 cm long T-shaped quartz tube which was heated in an air-acetylene flame using a 10 cm single slot burner. Argon (99.99%) was used as the purging gas; the flow rate was 0.5 lmin-l.390 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 Peristaltic - Acid solution To AA ectrometer Waste I Filter Valve in sample position Fig. 1 Diagram of the continuous flow hydride generator used for alkaline sample solutions A schematic flow diagram is shown in Fig. 1. Compared with the conventional configuration the hydrochloric acid and tetrahydroborate solution streams have been inter- changed the tetrahydroborate solution now acting as a 'blank' instead of the hydrochloric acid.Sodium tetrahy- droborate solution was also added to the alkaline sample solution. Both the blank and the sample solutions contained 0.4% sodium tetrahydroborate. The concentration of so- dium hydroxide in the sample solution was approximately 0.2 mol dm-3. Hydrochloric acid (4 mol dm-3) was used to acidify the alkaline sample solution and to generate the hydrides. The diameter of the peristaltic pump tubing was 0.5 mm for the hydrochloric acid and 0.8 mm for the other two streams giving flow rates of 3.2 and 7.2 mlmin-I respectively. In order to prevent particles from entering the hydride system the pump tubing carrying the sample was equipped with a G4 glass filter (pore size 5-1 5pm) at the inlet end.Reagents and Samples All reagents were of analytical-reagent grade and only de- ionized water was used. Sodium tetrahydroborate solution (3% m/v) was prepared by dissolving NaBH (Fluka) in 0.1 r n ~ l d m - ~ sodium hydroxide solution (Merck). The solution was filtered before use. A 4 mol dm-3 hydrochloric acid solution was prepared by dilution of the concentrated acid (37O/o Merck). A 1 .OOO g 1-l SeIV solution was prepared by dissolving 3.3308g of Na2Se03-5H20 (Fluka) in water and diluting to 1000 ml. Standard solutions of 2.5-3Opg 1-1 SeIV were prepared by diluting this solution further. The hydrogen peroxide solution was 30% (Merck). Three Standard Reference Materials (SRMs) with certi- fied values for selenium were obtained from the National Institute of Standards and Technology (NET) (formerly the National Bureau of Standards Gaithersburg MD USA).The samples were SRM 398 Unalloyed Copper V SRM 671 Nickel Oxide 1 and SRM 875 Cupro-Nickel 10 (CDA 706) (doped). Procedure Dissolution of copper metal Transfer 1 g of copper metal into a 100 ml beaker add 10 ml of 12 mol dm-3 hydrochloric acid and heat to 100 "C on a water-bath. Add 7.5ml of hydrogen peroxide in 0.5ml portions allowing the evolution of the gas to subside each time before adding a new portion. During this treatment leave the beaker on the water-bath. After dissolution cool and transfer the clear solution into a 250 ml calibrated flask and dilute to volume with water. Dissolution of nickel oxide and copper-nickel alloy Transfer 1 g of sample into a 100ml beaker and add in sequence 1 ml of hydrogen peroxide 10 ml of water and 10ml of hydrochloric acid (37Oh).Heat the solution to 100 "C on a boiling water-bath and add 3ml of hydrogen peroxide in 0.5 ml portions allowing the evolution of gas to subside each time before adding a new portion. After dissolution cool and transfer the clear solution into a 250ml calibrated flask and dilute to volume with water. Precipitation of copper and nickel Transfer a 1O.OOml aliquot from the 250ml flask into a 50 ml calibrated flask and add 5 ml of 3 mol dm-3 sodium hydroxide solution slowly with continuous swirling. Warm the precipitate formed on a water-bath at 100 "C for 1 h. After cooling add 6 ml of 3Oh sodium tetrahydroborate solution and dilute to volume (50 ml).Filter the solution through quartz wool (without washing the precipitate) and analyse the filtrate for selenium by the proposed method. Calibration The quantification is either by means of a calibration graph or a standard additions graph. The calibration graph is obtained using standard selenium solutions to which sodium tetrahydroborate is added so that the concentra- tion is the same as in the sample solution (0.4%). Alternatively a standard additions graph is obtained by adding 0 1 2 3 and 4 ml of a 0.5 mg 1-l SeIV solution to five 10ml aliquots of the dissolved sample which have been transferred into 50 ml calibrated flasks. To each flask 5 ml of 3 mol dm-3 sodium hydroxide solution are added slowly and the procedure described under Precipitation of copper and nickel is followed.Results and Discussion The dissolution of the samples with a mixture of hydro- chloric acid and hydrogen peroxide was preferred to oxidation with nitric acid because the excess of oxidant could then be removed easily by heating the solution. An excess of oxidant remaining would have resulted in the consumption of some of the tetrahydroborate solution added. The procedures for the copper metal and the nickel materials are somewhat different because it was found that the nickel materials reacted more vigorously with the acid than did the copper metal. In order to avoid the risk of losing selenium a milder treatment is used for the nickel materials. The dissolved sample was made alkaline with sodium hydroxide and sodium tetrahydroborate solution was added before the solution was diluted to volume.By using this procedure the subsequent filtration need not be quantitative which is advantageous because a quantitative filtration must involve a thorough washing of the precipi- tate. A washing step is time consuming and can lead to dilution of the sample solution. Apart from these considera- tions the tetrahydroborate solutions can as effectively be added after filtration and dilution to volume. Although not strictly necessary filtration of the solutions is recommended for two reasons. Firstly small particles of the precipitate can be introduced into the tubes of the hydride generator which involves the risk of a blockage. Secondly there is a possibility that the following unwanted reactions could take place after prolonged standing CuO(s) + Se2- + H20 3 CuSe(s) + 20H- Ni(OH),(s) + Se2- - NiSe(s) + 20H-JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL.6 39 1 Table 1 Determination of selenium in NIST Standard Reference Materials; units rng kg-I Reference materials Certified value Found S* n t SRM 398 Unalloyed Copper 17.5 4 0.8 17.3 1.4 5 SRM 875 Cupro-Nickel 4 5.4 0.5 7 SRM 671 Nickel Oxide 2.0 _+ 0.3 2.1 0.5 6 * s= Standard deviation. t n=Number of parallel digestions. However within the time-scale of this procedure no indication of these reactions was observed. For filtering quartz wool was found to be preferable to a glass or paper filter because of simplicity and speed. Glass wool proved less satisfactory because not all the particles were retained by the filter. The G4 glass filter mounted on the inlet end of the tubing carrying the sample was used only as an extra safety precaution.The results of the analyses of three NIST SRMs are given in Table 1. There is very good agreement between the results obtained and the certified values. This is true even for SRM 875 as the value given by NIST for selenium in SRM 875 is based on three widely differing results 2.5 mg kg-l obtained by atomic absorption spectrometry; 4.3 mg kg-l obtained by spectrophotometry with diamino- benzidine as the reagent; and lomgkg-l also obtained by spectrophotometry. No further details about the methods were given in the certificate; it is surprising that NIST established a certified value based on the cited results. As a curiosity it can be mentioned that the mean value of these results is 5.6mgkg-l which is close to the value of 5.4 mg kg-l that we obtained.The good agreement between our results and the certified values demonstrates that selenium is not coprecipitated when copper and nickel hydroxides are formed. The validity of both the standard calibration graph and standard additions graph (see under Experimental) was tested for all three materials. It was found that the standard additions graph was always parallel to the calibration graph indicating that the interference from copper and nickel is completely eliminated in the proposed method. Therefore a calibration graph can be used for quantification. The slope of the calibration graph was 0.0048 absorbance 1pg-l. No significant blank value was observed. Based on a signal to noise ratio of 2 the detection limit in the final solution was estimated as approximately 1 ,ug l-l which using this pro- cedure corresponds to about 1 pgg-l in the solid sample. In this work a continuous flow system was employed for convenience. However a batch system might also be used; in this instance hydrochloric acid is added as the final reagent. The method of generating hydrides from alkaline solu- tions is a novel approach. As shown in the present paper it can represent a useful alternative to the conventional acid solution method. References Bye R. J. Autom. Chem. 1989 11 156. Welz B. and Melcher M. Analyst 1984 109 569. Hershey J. W. and Keliher P. N. Appl. Spectrosc. Rev. 1989 25 213. Bye R. Engvik L. and Lund W. Anal. Chern. 1983 55 2457. Welz B. and Melcher M. Analyst 1984 109 577. Bye R. Analyst 1986 111 11 1 . Bye R. Anal. Chim. Acta 1987 192 1 1 5. Welz B. and Melcher M. Anal. Chim. Acta 1983 153 297. Paper I /00313E Received January 22nd I991 Accepted March 26th 1991

ISSN:0267-9477    

DOI:10.1039/JA9910600389

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 393 Characterization of Automotive Catalysts Using Inductively Coupled Plasma Mass Spectrometry Sample Preparation James A. Brown Jr. Frank W. Kunz and Ronald K. Belitz Ford Motor Company Research Analytical Sciences Department P. 0. Box 2053 Dearborn MI 48121 USA Several methods utilizing microwave energy induced dissolution were developed for rapid digestion and subsequent analysis of automotive catalyst material by inductively coupled plasma mass spectrometry (ICP- MS). Dissolution was accomplished within 2-3 h rather than days as with the widely accepted ashing methods. A comparison was made with several other ICP-MS techniques and the conventional wavelength dispersive X-ray fluorescence method. Keywords Micro wa we energy; acid dissolution; inductively coupled plasma mass spectrometry; automotive catalyst material; wavelength dispersive X-ray fluorescence A catalytic converter an attachment to the exhaust pipe is fitted to almost every new automobile in the USA in order to reduce pollution and to meet the requirements of a 1975 amendment to the Clean Air Act.The platinum group metals some of which are shown in Table 1 are used extensively in these catalytic systems and are often coated onto an alumina-based ceramic monolith or a metal monolith substrate. The over-all performance of these catalytic converters is highly dependent upon several factors namely the physical location within the exhaust system the surface area of the monolith and of most importance the precious metals loading ratio.The economical dispersion and subsequent recovery of these precious metals depends on their accurate determina- tion in the ceramic material at levels ranging from ppb upwards.' Inductively coupled plasma mass spectrometry (ICP-MS) is a fairly new technique for elemental and isotopic analyses. The technique combines the characteristics of the ICP for atomizing and ionizing injected material with the sensitivity of mass spectrometry. There are two unique advantages in the use of ICP-MS firstly the spectra are simple and interferences from inter-elemental effects are largely absent and secondly isotope abundance informa- tion is inherent in the m e t h ~ d . ~ ~ ~ Sample preparation is a critical step in any trace analysis procedure; frequently it is responsible for establishing the lower detection limit of an analysis through its influence on the analytical blank.This is particularly important in ICP- MS as the technique requires that the sample be in liquid form. Wet-digestion methods have gained widespread acceptance however they require close and constant attention by the analyst to avoid unintentional boiling over or evaporation of the sample to dryness. Digestion can often require 48 h to ensure complete dissolution. Thus a more rapid and effective digestion method for trace metal analysis has long been Microwave energy can be used to dissolve solid samples more safely and efficiently than traditional methods (i.e. 2-3 h). Oven-like heating devices are utilized instead of hot-plates for dissolving material for elemental analysis at trace levels i.e. ppm and lower. Microwave technology has two main advantages it is quick and it is relatively contamination free. These attributes are essential for reliable elemental trace analy~is.~-~ The objectives of this study were (i) to develop methods for the dissolution of monolithic ceramic automotive catalysts by microwave energy and subsequently to analyse the material quantitatively for trace elements by ICP-MS; (ii) to compare results from ICP-MS with wavelength dispersive X-ray fluorescence (WDXRF); and (ziz] to com- pare scanning with peak-jumping ICP-MS results. Experimental Reagents Elemental standards were prepared from reagents pur- chased from Spex Industries Edison NJ USA. Standard 1000 pg ml-l stock solutions were diluted in 1% HN03 to 10 pg ml-l working stock solutions which were then used for further appropriate dilutions.Aqueous calibration standards of 20,50 and 100 pg ml-l were prepared from the working stock solutions of precious metals. Table 1 shows the elemental components found in an automotive catalytic converter. The elements listed on the left represent ele- ments used to make the device whereas elements on the right of the table represent possible environmental contami- nants found in spent catalytic converters. Indium (100 pg 1-l) was used as an internal standard. All acids were Ultrex I1 Ultrapure reagents purchased from J. T. Baker Phillipsburg NJ USA. De-ionized water of 18 Mi2 cm-' resistivity was always used and was prepared using equip- ment obtained from Millipore Bedford MA USA.Instrumentation The ICP mass spectrometer used for this work was a VG PlasmaQuad PQ2+ system purchased from VG Instruments Danvers MA USA. Standard instrument parameters for the operating state are listed in Table 2. The WDXRF spectrometer used in this experiment was a fully automated Siemens Model SRS 303 with a ten- position sample changer. Matrix corrections for absorption and enhancement of the element-characteristic X-rays were made using the Artz method.* The operating parameters for the instrument are listed in Table 3. Apparatus All glassware was cleaned with a neutral detergent and rinsed with tap water to remove all of the detergent. It was then soaked in 50% HN03 for at least 24 h rinsed thoroughly with de-ionized water air dried and stored in sealed plastic bags in a closed cupboard.Microwave oven Digestion was performed in an MDS-81D system pur- chased from CEM Matthews NC USA.394 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 Table 1 Elemental components found in an automotive catalytic converter Environmental contaminants in Primary constituents spent devices Element Relative atomic mass Element Relative atomic mass Pt Rh Ce Ni Ba Pd La 195 103 140 58 137 106 139 Fe* 56 Pb 208 S* 32 P* 31 Zn 65 Mn 55 Ca* 40 * Problems for elemental ICP-MS analysis either because of interference or unfavourable ionization potential. Table 2 Standard instrument parameters for the operating state of the PlasmaQuad PQ2+ Parameter Setting ICP system- Forward power 1300 W Plate current 650 mA PA grid current at 1300 W 200 mA Reflected power <I0 w PA ioltage at 1300 W Filament voltage Cool gas flow Auxiliary gas flow Nebulizer gas flow Nebulizer gas pressure Sampling depth Sample cone orifice Skimmer cone orifice Skimmer spacing ring Extraction setting Collector setting L1 setting L2 setting L3 setting L4 setting Front plate setting Pole bias setting Low mass resolution Coarse resolution Fine resolution Cathode current at 0 u Cathode current at 300 u Grid current at 300 u Pulse discriminator Pulse (HT2) multiplier Pulse background Analogue multiplier Analogue offset Ex pan si on Intermediate Anal yser In teduce- Ion lenses- Quadrupole- Detector- vucuum- 4 kV 7.8 V 0.6 1 min-I 0.7 1 .min-' 138 kPa (20 psi) 12 mm 13 1 min-' 1.0 mm 0.7 mm 3.0 mm 1.0 7.7 7.7 5.4 5.0 3.8 8.0 6.0 5.00 3.00 5.00 10.00 mA 75.00 mA 0.0 mA 20.0 7.0 4.5 15.0 Hz 50.0 Hz 200 Pa 1 x Pa 1 x Pa Digestion vessel and capping station The digestion vessels used were made of PFA-Teflon [(perfluoroalkoxy)ethylene] purchased from CEM and fitted with relief valves.The vessels were rotated on a PFA- Teflon turntable during the digestion period to ensure Table 3 X-ray fluorescence operating parameters and sample preparation technique X-ray tube X-ray tube voltage X-ray tube current Sampling Sample size Sample grinding Sample containment Sample press Calibration Number of elements determined Cr 60 kV 50 mA Uses 3 samples (inner middle and 6.0 g 5 rnin ball mix 30 mm Somar No. 330 cap 18 tons in-2 for 30 s Single element standards using substrate material and outlet side of catalyst) 24 uniform heating of each sample.The caps were tightened in a capping station purchased from CEM to provide the uniform tightness required so that the relief valves vented at the same pressure in each vessel viz. 828 kPa (1 20 psi). The technique involves microwave heating of the materials when mixed with concentrated mineral acids (i.e. HN03 HCl and HF) so as to dissolve the material rapidly for suitable application to analysis by ICP-MS. The digestion vessels were cleaned by washing with detergent and rinsing with tap water then heating with 20 ml of concentrated HN03 in the microwave oven for 10 min at 100% power and finally rinsing thoroughly with deionized water. Method 1 Approximately 5.0 g of catalyst sample were ball-mixed in a Spex Model 8000 mixer-mill for 5 min using a Spex Model 8004 tungsten carbide vial-ball set producing a particle size of (400 mesh.This ball-mixed catalyst sample was dried in an oven at 100 "C weighed into a 120 ml PFA-Teflon digestion vessel containing 5 ml of HC1 and 5 ml of HF. The relief valves were placed on the PFA-Teflon vessels which were then sealed in the capping station. All of the samples were digested in the microwave oven for 5 min at 100% power (600 W) and left to stand for 10 rnin without power. They were then twice put through a cycle of cooling to room temperature digesting for 10 rnin at 100% power followed by standing for 10 rnin without power. After that the samples were cooled to room temperature transferred into poly- tetrafluoroethylene or quartz evaporation dishes and 5 ml of HC104 were added to each dish.The evaporation dishes were heated to HC1O4 fume on a medium temperature hot-plate cooled and 5 ml of aqua regia [HN03-HC1 (1 +3)] were added. All of the samples were then diluted to an appropriate volume and assayed by ICP-MS.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 395 Table 4 Comparative analysis of automotive catalyst material using WDXRF and ICP-MS techniques. Results given are the mean or mean +standard deviation (in ppm) for n= 18 determinations WDXRF Scanning Peak-jumping Element Laboratory 1 Laboratory 2 ICP-MS ICP-MS IMPd 1917 1 773 5 6 1938f31 1980+21 lo3Rh 373 366 f 7 431 + 14 397 k 5 140Ce 30 528 3 1 793 f 404 35471 +517 31 653f324 58Ni 22713 21 2492230 21 01 15656 23 953 f 385 56Fe 2 670 2 889 f 31 - 5 564 2 332 13'Ba 1951 1062k 13 1003f15 1 1402 15 Table 5 Comparative analysis of automotive catalyst materials using different microwave digestion methods.Results shown are the mean or mean 5 standard deviation (in ppm) for n = 18 determinations WDXRF ICP-MS Element Laboratory 1 Laboratory 2 PA* BAT lMPd 880 857 k 8 799 +_ 55 756k42 Io3Rh 180 185+5 189 5 6 141 + 3 I4OCe 28762 32 116f245 35 532 5401 20410 f 677 58Ni 20894 20275f 116 22 625 + 393 21 221 f 9 4 5 56Fe 2 693 3 132f 17 2 926 f 955 2 190+40 13'Ba 1905 991 f 9 1122+30 788 5 18 * PA Analysis after perchloric acid (HC104) digestion. t BA Analysis after boric acid (H3BO3) digestion. Method 2 Approximately 5.0 g of catalyst sample were ball-mixed and dried as outlined in Method 1.From the 5.0 g sample an aliquot of 0.5 g was transferred into a 120 ml PFA-Teflon digestion vessel and 6 ml of HN03 3 ml of HC1 and 2 ml of HF were carefully added. Relief valves and caps were placed on the vessels and each vessel was sealed in the capping station. The samples were digested for 3 min at 100% power and 15 min at 65Oh power. They were then cooled uncapped within the capping station neutralized with 89 ml ofH3B03 re-capped and digested at 100% power in the microwave oven for 10 min. The samples were cooled filtered and diluted as necessary for assay by ICP-MS. Results and Discussion In order for a method to be acceptable it must be demonstrated that the method produces results with good precision and with no evidence of significant bias.This work shows that the reproducibility of ICP-MS determina- tions is very good for the precious metals however there appear to be problems for some of the other metals especially Ce Ni Fe and Ba (see Tables 4 and 5). Precision is easily assessed but proof that the results are unbiased is not possible as the true result is unknown. It is possible however to provide evidence for the absence of significant bias in well controlled measurement systems which allow indvidual evaluation sources of systematic error.Z Good correlation was obtained between the scanning and peak- jumping ICP-MS results and the WDXRF analysis results (see Table 4). Good correlation was also obtained between the HClO. digestion and WDXRF results as can be seen in Table 5.The peak-jumping method detected Fe whereas scanning did not even after 18 determinations. Although ICP-MS is a sensitive technique for trace and ultra-trace elemental analysis singly charged elemental analyte ions are only measured with the quadrupole mass spectrometer. A large number of elements however pro- duce singly charged elemental analyte ions (M+) many form monooxides (MO+) some form doubly charged ions (M2+) and a few form hydroxide species (MOH+). Other polyions such as ARN+ and Am+ might also be formed. These analyte species are important because serious inter- element interferences can occur owing to spectral overlap.' This might account for discrepancies seen in Tables 4 and 5 in the values for Ce Fe and Ba.Boric acid digestion ICP- MS results (shown in Table 4) are consistently low suggesting that the sample was not completely digested. We believe that this can be corrected by adjusting the digestion time. This will be investigated further in the future. Conclusions The rapid relatively safe acid digestion methods devel- oped in this study are capable of complete dissolution of monolithic ceramic automotive catalytic material. The material is sufficiently digested to allow trace element analysis by ICP-MS. The microwave energy utilized in these procedures can completely digest this material in 2-3 h rather than 1-2 d as for the widely accepted ashing methods. The ICP-MS results especially for precious metals compared favourably with those obtained from WDXRF. The ICP-MS peak-jumping technique appears to be the method of choice as the operation time is halved. Development work is being carried out to produce digestion procedures that are even more efficient. References Westwood L. C. and Lu Y. T. personal communication. Houk R. S. and Thompson J. J. Mass Spectrom. Rev. 1988 7 425. Okamoto K. and Fuwa K. Anal. Chem. 1984,56 1758. Nadkarni R. A. Anal. Chem. 1984,56 2233. Kingston H. M. and Jassie L. B. in Introduction to Microwave Sample Preparation Theory and Practice American Chemical Society Professional Reference Book Washington DC 1989. Kingston H. M. and Jassie L. B. Anal. Chem. 1986 58 2534. Vaughn M. A. and Horlick G. Appl. Spectrosc. 1986 40 434. Artz B. A. X-ray Spectrom. 1977 6 165. Paper 0/04 781 C Received October 23rd. I990 Accepted March 20th. I991

ISSN:0267-9477    

DOI:10.1039/JA9910600393

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 397 Direct Analysis of Slags by Inductively Coupled Plasma Atomic Emission Spectrometry Using Slurry Sample Introduction Techniques Maria Luisa Fernandez Sanchez Ben Fairman and Alfred0 Sanz-Medel* Department of Physical and Analytical Chemistry Faculty of Chemistry University of Oviedo 33006 Oviedo Spain A practical method is described for the direct determination of Si Ca Mg Al Fe Mn Ti Na and K in slag samples by the introduction of sample suspensions into the inductively coupled plasma atomic emission spectrometer. The effect of the particle size distribution on the atomization efficiency of these elements when slurries of the slag samples were aspirated into the plasma has been studied. The slurry samples were prepared by dispersing 0.1 g of ground slag in 100 ml of 0.35% ammonia solution; calibration was achieved by the use of a reference slag prepared in the same manner.The results obtained for the direct analysis of slag slurries using such a procedure were in good agreement with those obtained by classical dissolution of the sample. The reproducibility of the results with slurry nebulization (concentration range 1.7-5.5'/0) were poorer than those observed with aqueous solutions (concentration range 0.5-4.8%) but were acceptable for slag industrial control. Keywords Elemental slag analysis; slurry atomization; inductively coupled plasma atomic emission spec- trometry An important limitation of the otherwise popular induc- tively coupled plasma (ICP) as a source for atomic emission spectrometry (AES) is that a conventional ICP technique requires the sample to be in solution.Because of this the sample preparation time in many solid sample analyses often exceeds the analysis time by unacceptable lengths. This means that the potential analytical speed of ICP-AES cannot be fully realized unless alternatives to the classical time-consuming and sometimes hazardous dissolution methodologies can be developed. Hence the considerable interest in recent years in investigations into the possibili- ties of direct analysis of solid samples. Perhaps one of the most interesting approaches to solid sampling in atomic spectrometry is slurry injection,' that is the introduction of aqueous (or organic) suspensions of fine powders or finely ground materials using a high solids nebulizer.When suspensions are nebulized into the ICP the atomization efficiency is mainly dependent on the sample transport efficiency which in turn is a function of the particle size and sample matrix. The application of slurries as a sample introduction technique to the ICP has been successfully reported by several workers for the determina- tion of a variety of elements in soil^,^^^ geological material~,~J~ clay," kaolin12J3 and refractory Watson and MoorelS used an ion-exchange resin to concentrate noble metals from a dissolved sample and the loaded resin was then mixed with water to form a slurry that was introduced into the ICP. Sugimae and Mizoguchi16 intro- duced suspensions in an organic medium into the ICP. The use of reference materials in slurry form as a calibration procedure for slurry atomization has also been rep~rted.~J' Watson17 used an internal standard of Li4B407 plus 1% Sc203 and used reference ores and slags in order to obtain calibration functions. Halicz and Brenner9 employed a similar technique using Sc as the internal standard and calibration was performed by using the ratios of the analyte to scandium internal standard reference signals as a function of the concentration of the reference material slurry.The application of a flow injection manifold for the introduction of slurries into an ICP has also been reported recently. * * To whom correspondence should be addressed. Blast furnace slag is a by-product obtained in the manu- facture of iron. The bulk of the slag consists principally of silica alumina and lime with minor amounts of magne- sium oxide iron oxide and alkali oxides.This by-product is used in road building and fertilizers but the cement industry is by far the largest user of the blast furnace slag. The slag can be used in the production of cement in two basic ways (i) as a raw material for cement manufacture; or (ii) as a cementitius material combined with portland cement. The activity of the slag used in cement or concrete is determined by its composition and by the rate at which the molten material is cooled when it comes from the furnace. The slag can be added to the cement in order to reduce the cost or to modify the performance (ie. to produce concrete that is relatively resistant to certain types of chemical attack such as those from sulphate or sea- water) .In this paper a method is described using compromise conditions for the routine multi-element determination of Si Ca Mg Al Fe Mn Ti Na and K in slag samples by slurry atomization ICP-AES. The optimum operating para- meters in the ICP and the influence of particle size on the analytical signal were investigated. The effect of different dispersants on the stability of the slag suspension and the influence of the solids content on the analytical signal were also studied. Experimental Apparatus A Perkin-Elmer Model 5000 ICP spectrometer was used. The source and spectrometer characteristics are described in Table 1. A high-solids polytetrafluoroethylene Babing- ton-type nebulizer19 with a double-pass spray chamber was used for sample introduction. The slurry sample was delivered to the ICP nebulizer through a 0.8 mm i.d.plastic tube using a peristaltic pump. The ICP operating para- meters selected for the slag analysis are also listed in Table 1. Particle size analysis was carried out using a photosedi- mentometer (Lumosed Retsch). Sample Dissolution Procedure Slag samples previously hand-ground and dried were dissolved by weighing 0.1 g of the sample into a Teflon398 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 2.0 1.5 1 .o 0.5 Table 1 Instrumentation and plasma operating conditions Spectrometer- Sequential scanning (0.03 nm bandpass Holographic ultraviolet grating Fassel-fused silica torch 2 kW 27.12 MHz High-solids Babington-type nebulizer Coolant flow rate Auxiliary flow rate Injector flow rate Nebulizer pressure Observation height Plasma power ICP source- Plasma operating conditions- 16 1 min-' 0.8 1 min-I 0.6 1 min-I 193 kPa 16 mm 1.25 kW I -12 I / B I - 0 ' I 1 1 ' 0 0.9 1.0 1.1 1.2 1.3 1.4 1.5 R.f. power/kW bomb and adding 5 ml of water 1 ml of HF and 3 ml of aqua regia (3 + 1 HCl + HN03). The bomb was heated in an oven at 140 "C for 45 min and then left to cool. Ten ml of a saturated solution of boric acid were added and the bomb was re-sealed and heated to 120 "C for another 20 min. After cooling the solution was transferred into a 250 ml calibrated flask and diluted to volume with distilled de- ionized water. Slurry Sample Preparation The original slag samples were dry-ground in a ball-mill (Pulverisette Model 6 Fritsch) to a size that allowed them to pass through a 37 ,um sieve.The particle size of the sieved sample was further reduced down to (10 pm by wet- grinding* as follows 0.1 g of the sample was added to 30 ml polyethylene bottles containing 1 g of 3 mm zirconium oxide beads and 0.5 ml of water and ground by shaking for 3 h in a laboratory flask shaker. The resultant slurry was transferred into a 100 ml calibrated flask and diluted to the mark with 0.35% v/v ammonia solution. The slurry was then placed in an ultrasonic bath for 15 min. A magnetic stirrer was used to agitate the sample while it was pumped into the ICP in order to maintain a uniform slurry of the slag. - 6 8 10 12 14 16 18 20 22- Observation height/mm 25 20 - 15 - 10 1.0 - 0.5 - - 5 B o c o s 4 - 0 " ' a ' ' ' a * r Q 0 20 22 24 26 28 30 32 34 36 38 40 42 Gas pressure/psi Results and Discussion Plasma Operating Conditions for Slag Slurries The analytical emission lines selected (see Table 2) for the determination of Si Ca Al Mg Fe Mn Ti Na and K in slags by ICP-AES were selected from the literature20 and from previous preliminary work with slag s1urries.2*~22 The influence of the more critical operating parameters of the ICP on each analytical line when using slurry samples prepared as above were studied by investigating the signal- to-background (S/B) ratio observed as a function of the viewing height above the load coil; the plasma power Fig.1 Effect on A the emission intensity of Mn B the background emission intensity and C the signal to background ratio of a ground slag slurry as a function of (a) r.f.power; (b) observation height; and (c) nebulizer gas pressure applied; and the nebulizer gas flow. This last parameter should be the most critical as the injector gas flow not only affects the efficiency of the nebulization but also determines the sample residence time in the plasma channel. The results obtained showed that generally the signal and the background increased with increasing power and decreased with increased viewing height and nebulizer gas flow. As an example the results for Mn are illustrated in Fig. l(a)-(c) which also show the effects of these parameters on the S/B ratios. The best SIB ratios for Si Ca Mg and Mn were observed at low observation heights low gas flows (longer residence time in the plasma) and high radiofrequency (r.f.) power.In contrast the best SIB ratios for Na and K were observed for high observation heights and low power whereas the optimum results for Al Fe and Ti were obtained using an intermediate observation height and r.f. power and high gas flows. The optimum operating parameters observed for Table 2 Optimum experimental conditions for each element of interest Nebulizer Wavelength/ Observation gas flow/ Plasma Element nm height/mm ml min-' power/kW Si 288.15 10 0.64 1.30 Ca 3 17.93 12 0.5 1 1.40 279.55 9 0.47 1.40 A1 396.15 12 0.64 1.10 Mg Fe 259.94 14 0.64 1 .oo Mn 257.61 10 0.5 1 1.30 Ti 334.94 14 0.69 1.10 Na 589.59 26 0.64 0.90 K 766.49 26 0.60 1 .ooJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL.6 399 1.0 0.8 0.6 0.4 0.2 the excitation of a slurry of a sample in an ICP are given in Table 2 for each element studied. A simplex technique was used to determine the optimum conditions for each element.23*24 For multi-elemental analysis a set of com- promise conditions were chosen and the values finally used are given under plasma operating conditions in Table 1. - - - - - A n- Particle Size The most critical parameter in slurry atomization is probably the particle size distribution of the ~ample.~*'*~J~ In the particle size investigations 15 g of sample were ground in the ball-mill for increasing periods of time and different size fractions were isolated using a series of sieves (by manual agitation of the sieves). It was observed as expected that suspensions prepared from different particle size ranges (180-63,63-37 and (37 pm) produced drama- tically different emission intensities for all of the elements studied.This effect for three important elements viz. Si Ca and A1 is shown in Fig. 2. Only when the particle size of the slag was reduced to <37 pm could analytically useful signals be observed in the system. It was verified that 2.5-3 h of grinding in the ball-mill ensured that all the sample passed through a 37 pm sieve. Williams et aZ.* described an effective method for the rapid reduction of the particle size by shaking the coarse slurry samples with Zr02 beads in polyethylene bottles. The use of such a technique was tested by shaking the sieved slag sample for 0.5 and 3 h with a laboratory flask shaker.The measured particle size distribution of these two fractions is shown in Fig. 3. The figure shows how effective the use of Zr02 beads during grinding can be in reducing the mean particle size of the slag samples. In fact the mean particle size diameters were 4 and 2 pm after 0.5 and 3 h of grinding with ZrOl beads respectively. Particle size distri- bution analysis showed that more than 90% of the particles were below 22 pm after 0.5 h and below 5 pm after 3 h of grinding with Zr02 beads. After the particle size reduction studies the relation between the particle size distribution in the slurry and the analyte emission intensity observed in the ICP was investi- gated slag slurries (0.1 % m/v) were prepared from each of the three sieved fractions.They were as before 180-63 63-37 and t 3 7 pm and were subsequently analysed for Ca Fe Ti and Na by ICP-AES. The results obtained (as illustrated for Ca Fe Ti and Na in Fig. 4) show that the Ca A1 1.2 C Particle size fraction Fig. 2 Effect of different particle size fractions on the emission intensity of Si Ca and Al A 180-63 ,urn; B 63-37 pm; and C (37 pm 100 5-10 10-15 15-20 20-25 2g30 Particle size/pm Fig. 3 Effect of grinding time upon the particle size distribution of slag slumes using the wet Zr02 bead method unshaded area 0.5 h; and shaded area 3 h Ti 1.8 Ca Fe 1.6 3 1.4 s 1.2 CI .- C $ g J 1.0 .- 3 0.8 . 0.6 0 2 0.4 E w 0.2 Q) c. .- .- n v Particle size fraction Fig. 4 Effect of slag particle size upon the emission intensity of Ca Fe Ti and Na A before sieving (1 80-63 ,urn); B after sieving (63-37 pm); C after sieving and wet grinding with ZrO beads (<37 ,urn) simple sieving of the sample can double the signal (e.g.the emissions from fractions A and B for Ca). All of the analyte signals were increased further by grinding with Zr02 beads but the magnitude of the increase was not equal for each of the different elements under study for instance the Ti and Na emissions show a higher percentage increase with wet- grinding than the Fe emission signal (compare B and C fractions in the oberved signals in Fig. 4). The relationship observed between the Zr02 grinding time and the analyte intensities for all of the elements under study is illustrated in Fig. 5. The signal increases with grinding time (as smaller particles are produced with extended grinding which in turn affects the solid transport 2 f 2 1.0 2 1.5 .- - .- fn Q) U .- 0.5 0 fn .- .- E n - - w Time Fig.5 Effect of grinding time using the wet ZrO bead method upon analyte emission intensity from slag slurries unshaded area 0.5 h; and shaded area 3 h400 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 efficiency). However the emission intensity did not in- crease to the same extent for the different elements. This indicates that the slag is a multicomponent material and that the different degrees of hardness of each of the components has resulted in different particle size distribu- tions for each mineral. Selection of Dispersant The use of a dispersant helps to maintain the small particles of a slurry sample in suspension.In order to achieve a stable suspension of ground slag the dispersants tested were Triton X- 100 sodium pyrophosphate (Na4P207) and am- monia solution. The effect of the dispersants was investi- gated using slurries (0.1 Oh d v prepared with each of the dispersants) which were aspirated into the ICP. The stability of the observed analyte signals was determined over a period of 6 min. The results showed that in suspensions prepared in 0.02 0.1 1 or 2% m/v Triton X- 100 a depression of the signal was evident and the stability of the signals was poor. A slurry prepared in 0.1Oh m/v Na4P20 showed good stability when monitoring the emis- sion lines of Ca and Mg. The ammonia solution (0.35% v/v) as found by Ebdon and Collier for kaolin slurries,13 proved to be the most effective dispersant for the fine slag particles as it produced the most stable emission signals for all of the elements under examination.Effect of Solids Content in the Suspension In order to evaluate the influence of the percentage of solid present in the suspension on the ICP emission signal intensity slurry calibration graphs were obtained by vary- ing the concentration of solids in the slag slurry (from 0.05 to 0.5Oh d v ) . The results obtained are shown in Fig. 6. The intensity increases linearly with the amount of slag in the slurry in all instances except for Mg where the observed response was not linear above 0.2% d v . This can be attributed to self-absorption phenomena which were also detected in aqueous solutions of Mg2+ with concentrations similar to those of the slag slurry (at 0.2% m/v).Analytical Application When the slag slurry was analysed by ICP using aqueous standards and using the slurry preparation as detailed (k 3 h grinding with Zr02 beads) the recoveries (as calculated from the slurry to aqueous solution signal ratio) ranged from 60 to 8O% depending on the analyte. It was thought 0.1 0.2 0.3 0.4 0.5 C Concentration of solids (% m/v) Fig. 6 The effect of solid concentration upon the emission intensity of A; Si Ca Al Fe Ti Na and K; and B Mg in a slag slurry Table 3 Comparison of elemental content of a slag as determined by the slurry technique and by acid digestion. Each value is the mean of 3 determinations with a 1 s integration time Acid digestion Slurry atomization Oxide Content (%) RSD (Oh) Content (%) RSD (%) Si02 CaO MgO Fe203 A1203 Mn02 TiOz Na20 KZ0 40.99 8.66 4.10 3.16 0.43 0.91 2.52 0.22 0.56 0.5 0.6 0.8 0.9 1.3 1.5 1.2 1.3 4.8 41.15 8.54 4.40 3.14 0.38 1.02 2.54 0.16 0.50 1.7 2.5 1.2 2.1 5.2 1.8 1.4 3.7 5.3 that these low recoveries might be due to transport losses of the slag slurry aerosol in the commercial spray chamber and possibly incomplete atomization andor excitation in the As shown previously by other w o r k e r ~ ~ * ~ ~ ~ J ~ poor reco- veries are related to particle size.A particle size distribution of < 5 pm (see Figs. 3 and 5 ) should overcome this problem but at the expense of unacceptably long grinding times. Therefore a more practical approach was finally selected the sieved sample was ground for 30 min with Zr02 beads (a more reasonable period than 3 h for routine determina- tions); and the loss in sensitivity was compensated for by using a reference slag (in slurry form) in order to calibrate the ICP. As described above this method of calibration for slurry samples has been used by several workers notably Sugimae and Mizoguchi for airborne particles,16 and Halicz and Brenner for various geological material^.^ These work- ers found that close matching of sample and standard suspensions was vital for correct calibration.Although Sugimae and Mizoguchi concluded that differences in the response to the iron present in air particles between samples and reference standards was mainly due to the particle size composition Halicz and Brenner in addition stressed that the textural mineralogical and chemical compositions must also be similar.For the present investi- gation this was achieved by the use of the slag reference material Slagg SI-Ss (Institutet fur Metallforskning Ger- many) which underwent the same treatment as the samples so as to satisfy the conditions mentioned above. The total concentration of Si Ca Al Mg Fe Ti Mn Na and K obtained by the direct analysis of slag suspension by ICP are given in Table 3. These results are comparable in terms of accuracy and precision with those obtained by the acid digestion method described above. Good agreement is also observed between the results obtained by both methods (direct analysis by slurry atomization and the acid digestion of the sample). However the precision is worse when the slag slurry is introduced into the ICP.For routine analysis the poorer precisions observed with the slurry technique are more than compensated for by simplicity and speed of operation which reduces the analysis time the risks of contamination and loss and the use of hazardous chemi- cals when compared with classical acid dissolution. ICp.7.12,14 Conclusions Direct solids analysis for the total concentrations of Si Ca Mg Al Fe Mn Ti Na and K in slags by ICP-AES is possible by nebulizing suspensions of each. As previously s ~ o w ~ ~ * ~ ~ ~ J ~ the most critical factor affect- ing the ICP signal has proved to be the particle size of the ground slag generally the ICP analytical signals increase with a reduction in the particle size distributions of theJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL.6 40 1 slurries. The longer the grinding time the closer the emission signals of slurries come to those of aqueous solutions containing an equivalent concentration of the analyte being studied. By using the proposed procedure the ratios between the two emission signals as stated earlier were always below 1.0 (normally between 0.6 and 0.8 depending on the analyte). This variability demonstrates the complexity of the multicomponent nature of the slag material and points to preferential particle size reduction depending on the hardness of each mineral component when the longer wet-grinding times are not used. On the other hand when the solid content in the slurry was increased from 0.05 to 0.5% m/v no viscosity effects were observed.Therefore the reduced recoveries observed are perhaps due to less effective transport of the slag slurry from the nebulizer to the ICP as compared with aqueous solutions in addition to the possibility of incomplete volatilization and/or atomization (the extent of which would be mineral or element dependent).I4 As found by other workersgJ6 these phenomena necessitate the use of slag reference materials in the form of slurries instead of aqueous solutions for the calibration of the instrument. The results obtained show that the slurry technique holds promise for the direct and accurate analysis of solid slags by ICP-AES and with the calibration limitation detailed above offers a straightforward non-hazardous technique for monitoring both major and minor elements in routine slag analysis.References Fuller C. W. Hutton R. C. and Preston B. Analyst 1981 106 913. Wilkinson J. R. Ebdon L. and Jackson K. W. Anal. Proc. 1982 19 305. Ebdon L. and Wilkinson J. R. J. Anal. A t . Spectrorn. 1987 2 39. Ebdon L. and Wilkinson J. R. J. Anal. A t . Spectrom. 1987 2 325. 5 McCurdy D. L. and Fry R. C. Anal. Chem. 1986,58,3126. 6 Ebdon L. Foulkes M. E. Parry H. G. M. and Tye C. T. J. Anal. At. Spectrom. 1988 3 753. 7 Dick W. A. Page J. R. and Jewell K. E. Soil Sci. 1985,139 21 1. 8 Williams J. G. Gray A. L. Norman P. and Ebdon L. J. Anal. At. Spectrom. 1987 2 469. 9 Halicz L. and Brenner I. B. Spectrochim. Acta Part B 1987 42 207. 10 Verbeek A. A. and Brenner I. B. J. Anal. At. Spectrom. 1989 4 23. 11 Speirs G. A. Dudas M. J. and Hodgins I. W. Clays Clay Miner. 1983 31 397. 12 Ebdon L. and Collier A. R. Spectrochim. Acta Part B 1988 43 355. 13 Ebdon L. and Collier A. R. J. Anal. At. Spectrom. 1988 3 557. 14 Ebdon L. Foulkes M. E. and Hill S. J. Anal. At. Spectrom. 1990 5 67. 15 Watson A. E. and Moore G. L. S. A). J. Chem. 1984,37,81. 16 Sugirnae A. and Mizoguchi T. Anal. Chim. Acta 1982,144 205. 17 Watson A. E. S. Afr. J. Chem. 1986 39 147. 18 Ambrose A. J. Ebdon L. Foulkes M. E. and Jones P. J. Anal. At. Spectrom. 1989 4 219. 19 Ebdon L. and Cave M. R. Analyst 1982 107 172. 20 Boumans P. W. J. M. Line Coincidence Tables for Inductively Coupled Plasma Emission Spectrometry Pergamon Press Oxford 1980. 21 Fernindez Sdnchez M. L. Palacio Suarez J. Ferndndez Molina E. and Sanz-Medel A. J. Anal. At. Spectrom. 1987,2 491. 22 Fernindez SAnchez M. L. PhD Thesis University of Oviedo 1989. 23 Garcia Alonso J. I. PhD Thesis University of Oviedo 1985. 24 Ebdon L. Cave M. R. and Mowthorpe D. J. Anal. Chem. 1980 115 179. Paper 0/0262 1 B Received June 12th 1990 Accepted March I9th I991

ISSN:0267-9477    

DOI:10.1039/JA9910600397

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 403 Abell Ian 145 Abollino O. 119 Ali Abdalla H.. 2 1 1 Andersen Knut-Jan. 277 Apte S. C. 169 Barnes Ramon M.. 57 Baxter Douglas C. 109 Belitz Ronald K.. 393 Bendicho Carlos 353 Beinrohr Ernest 33 307 Berglund Ingemar 109 Berman Shier S. 19 283 Blades Michael W.. 2 15 Blais. Jean-Simon 225 Blue James L. 26 1 Branch Simon 15 I 155 Bridenne Martine 49 Brindle Ian D. 129 Brindle Mary E.. 129 Brown James A.. 393 Butcher David J. 9 Butler L. R. P. 329 Bye Ragnar 389 Canals Antonio I39 Carbonell Vincente 233 Carre Martine 49 Cervera M. L. 379 Chen Hengwu 129 Chou Lei 273 Collins C. S. 329 Comber S. D. W. 169 Corns Warren T.. 155 Cskmi Pavol 307 Dawson John B. 93 de la Guardia Miguel 233,379 de Loos-Vollebregt Margaretha T.C. 165 323 353 Dim de Rodriguez Olga 49 Dittrich Klaus 3 13 Ebdon Les 15 I 155 CUMULATIVE AUTHOR INDEX FEBRUARY-AUGUST 1991 Fairman Ben 397 Fang Zhaolun 179.30 1 Fernandez Sanchez. Maria Luisa. Forbes Kimberely A. 57 Ford Mick I5 1 Foulkes Mike IS I Franks Jeff 145 Frech Wolfgang 109 Fuchs Holger 3 13 Furata N. 199 Garden Louise M. 159 Gardener M. J. 169 Gervais Lyne S. 41 Gunn. A. M. 169 Hang Heng-bin 385 Hassell D. Christian 105 Haswell S. J. 339 He Bin 385 Hernandis Vincente 139 Hieftje G. M. 191 Hill Steve 155 Hoenig Michel 273 Holcombe James A. 105 Huang Degui 2 15 Huang Min 22 1 Huyghues-Despointes Alexis 225 Igarashi Yasuhito 205 335 Irwin Richard L. 9 Ishii Izumi 3 17 Jiang Zucheng 22 1 Julshamm. Kaare 277 Kibble Helen A. B. I33 Kim Chang-Kyu 205 Kluckner Paul D.37 Kunz Frank W. 393 Larsen. Erik H. 375 Le Xia-chun 129 Ledingham Kenneth W. D. 73 Li Ang 385 Littlejohn David 159 397 Lund Walter 389 Luong Van T. 19 L’vov. Boris 191 Maage Amund 277 Majidi Vahid 105 Marot Yves. 49 Marshall John 145 159 Marshall William D.. 225 Masuda Kimihiko 335 Matusiewicz Henryk. 283 McInroy James F. 335 Mentasti E. 119 Mermet. Jean-Michel 49 3 13 Michel. Robert G. 9 Millward Christopher G. 37 Miyazaki Akira 173 Momplaisir Georges Marie 225 Montaser Akbar. 3 17 Montoro R. 379 Mora Juan 139 Morita. Shigemitsu 205 Mukhtar S. 339 Ng Kin C. 2 1 I Ni. Zhe-ming 385 Offley Stephen G. 133 O’Neill Peter 151 155 Parsley David H. 289 Peng Runzhong 165 Poluzzi Vanes 33 Porta V. 1 19 Prell Laurie J. 25 Rademeyer. Cor J. 329 Rapta Miroslav 33 Redfield David A 25 Regnier Pierre 273 Reszke Edward E.57 Rivii.re Brigitte. 3 13 Rowbottom William H. 123 Salin Eric D. 41 Salvador Amparo 233 Sampson Barry I15 Sanz Angel 233 Sanz-Medel Alfredo 397 Sarzanini C. 1 19 Seare Nichola J. 133 Seki Riki 205 Shiraishi Kunio 335 Singhal Ravi P. 73 Slavin Walter 191 Sperling Michael 179,295,301 Stratis. John A. 239 Sturgeon Ralph E. 19 283 Styris David L. 25 Taddia Marco 33 Takahashi Junichi 9 Takaku Yuichi 205 335 Tan Hsiaoming 3 17 Tanaka Gi-ichiro 335 Tao Hiroaki 173 Tiggelman Johan J. 165,323 Travis John C. 261 Tsumura Akito 205 Turk Gregory C. 261 Tye Chris 145 Tyson Julian F. 133 307 Uden Peter C. 57 Vanhoutte C. N. 32 3 Watters Robert L. Jr. 261 Welz Bemhard 179,295,30 1 Wickstr~m Torild 389 Willie Scott N. 19 Winefordner James D. 2 I I Xu Fu-zheng 385 Yamamoto Masayoshi 205 Yamasaki Shin-ichi 205 Ybaiiez N. 379 Y in Xuefeng 295 Yoshimizu Katsumi 335 Yu Li-Jian 261 Zachariadis George A. 239 Zeng Yun’e. 22 1

ISSN:0267-9477    

DOI:10.1039/JA9910600403

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

1992 Winter Conference on Plasma Spectrochemistry January 6 - 11 1992 San Diego California The I992 Winter Conference on Plasma Spectrochemistry seventh in a series of biennial meetings sponsored by the ICPlnformation Newsletter features developments in plasma spectrochemical analysis by inductively coupled plasma (ICP) dc plasma (DCP) microwave plasma (MIP) and glow and hollow cathode discharge (GDL HCL) sources. The meeting will convene Monday January 6 through Saturday January 11,1992 at the San Diego Princess Convention Center in San Diego California. Continuing education short courses at introductory and advanced levels will be offered Friday through Sunday January3 - 5. A three-day exhibition of spectroscopic instrumentation and accessories also will be presented. Objectives and Program The rapid growth in popularity of plasma sources for atomization and excitation in atomic spectroscopy and ionization in mass spectrometry and the need to discuss recent developments of these discharges in spectrochemical analysis stimulated the organization of this meeting.The Conference will bring together international scientists experienced in applications instrumentation and theory in an informal setting to examine recent progress in the field. Approximately 500 participants Ram 25 countries are expected to attend. Approximately 200 papers describing applications fundamentals and instrumental developments with plasma sources will be presented in lecture and poster sessions by about 150 authors. Symposia organized and chaired by recognized experts will include the following topics 1) Sample introduction and transport phenomena 2) Flow injection spectrochemical analysis 2) Automation and plasma instrumentation including chemometrics expert systems on-line analysis software and remote-system automation 3) Sample preparation treatment and automation 4) Glow and hollow cathode discharges 5) Laser-assisted plasma spectrometry 6) Excitation mechanisms and plasma phenomena 7) Plasma source mass spectrometry 8) Spectroscopic standards and reference materials and 9) Plasma spectrometric detection in chromatography.Six plenary and 16 invited lectures will highlight advances in these areas. Three afternoon poster sessions will feature applications automation and new instrumentation. Five panel discussions will address critical development areas in sample introduction automation treating difficult samples practical plasma source mass spectrometry and plasma source chromatographic detectors.Plenary invited and submitted papers will be published in September 1992 in the Journal of Analytical Atomic Spectrometry as the official Conference proceedings after peer review. Instrument Exhibition A three-day exhibition of spectroscopic instrumentation and chemicals electronics glassware publications and software supporting plasma spectroscopy will complement the scheduled sessions on Tuesday through Thursday January 7 - 9 with approximately 30 firms participating. Invited Speakers Invited speakers include M. Blades M. Borsier P. Boumans J. Broekaert S. Caroli M.B. Denton K.Dittrich M.F. Gin6 W. Harrison G. Hieftje G. Horlick R.S. Houk J. Hubert L. Jassie K. Jinno H. Kawaguchi G. Knapp J. McLaren J.M. Mermet H. Ortner J. Ruzicka and E. Voigtman. Continuing Education Short Courses Introductory and advanced four-hour short courses will be presented Friday thrFgh Sunday January3 - 5. Designed to provide background and intensive training in popular topics of plasma spectrochemistry these courses feature analysis methods instrumentation and sample introduction. Social Activities The Conference will be held at the San Diego Princess on Vacation Isle in Mission Bay 10 minutes away from the San Diego International Airport. San Diego combines the proximityof Mexico with internationally famous landmarks including the San Diegozoo Balboa Park Sea World Cabrillo National Monument Mission Bay Aquatic Park San Diego Harbor Old Town Wild Animal Park and Saipps Aquarium.Disneyland is only 90 miles to the north and Tijuana Mexico is approximately 30 miles to the south. The America's Cup '92 selection trials will be held in San Diego in mid- January. The average high temperature in January is 65°F. A Conference social evening on January 7 will feature a dinner and show. Daily social hours and refreshments also are planned. Accommodations and Travel Central Travel Springfield Massachusetts is the official Conference travel agency. Accommodations at the Sen Diego Princess where all Conference activities will take place can be reserved with Central Travel at a special Conference rate of $90 per day (excluding tax) before October 18.After that a late fee will be charged. Arrangements for families with children are provided and extended stays before and after the Conference are offered at the Conference rate. Special low fares on United Airlines and discount automobile rentals are available exclusively through Central Travel. For travel information and reservations please contact Central Travel at 800-777-1680 (US) or 413-781 -1680; fax 41 3-737-9772. Registration The Conference registration fee includes a copy of the Conference proceedings Conference abstracts and a souvenir tee shirt. The registration fee is $260 prior to October 18 $375 until December 23 and $450 thereafter. Discounts are provided for students and no registration fee is required for spouses. Short-course preregistration fee is $75 prior to October 18 $1 10 until December 23 and $155 afterward for ea& four-hour short course.Further Information For further information and registration materials contact 1992 Winter Conference on Plasma Spectrochemistry Attention Ramon Barnes Department of Chemistry 102 LGRC Towers University of Massachusetts Amherst MA 01 003-0035 USA.(413) 545-2294 fax (41 3) 545-4490. Details concerning exhibitor registration facilities fees and advertising rates also are available upon request.11 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 1992 Winter Conference on Plasma Spectrochemistry San Diego California January 6 - 11,1992 Preliminary Program Monday January 6,1992 1. Flow Injection Spectrochemical Analysis Julian F.Tyson Chairman 8:OO OPENING. Ramon M. Barnes University of Massachusetts Department of Chemistry Lederele Graduate Research Center Amherst MA 01003-0035 8:05 WELCOME. Velmer A. Fassel Ames Laboratory Institute for Physical Research and Technology Iowa State University Ames LA 5001 1-3020 8:lS PL1 NEW TOOLS AND DIRECTIONS IN SPECTROCHEMICAL ANALYSIS - 1992. M. Banner Denton University of Arizana Department of Chemistry Tucson AZ 85721 9:lS Break 9:30 IL1 ENHANCEMENT OF ATOMIC'SPECTROSCOPY BY FLOW INJECTION TECHNIQUES. Jaromir Ruzicka University of Washington Center for Process Analytical Chemistry MS BG-10 Seattle W A 98195 1000 IL2 MULTIPURPOSE FLOW INJECTION SYSTEM. 1. PROGRAMMABLE DILUTIONS AND STANDARD ADDI- TIONS FOR ICP-AES. Boaventura Freire dos Reis Maria Fernanda Gin& Francisco Jose Krug and Henrique Bergamin Filho Centro de Energia Nuclear na Agricultura Av.Centenhi0 303 C.P. 96 CEP 13400 Piracicaba SP Brasil 1030 M1 OFF-PEAK BACKGROUND CORRECTION OF TRANSIENT SIGNALS. Brenda Caughlin and Henk Blok Chemex Labs Ltd. 212 BrooksM Avenue North Vancouver BC V7J 2C1 Canada 1050 M2 A HYBRID FIA-DIRECT SAMPLE INSERTION SYSTEM FOR ONE HUNDRED FOLD IMPROVEMENT OF DETECTION LIMITS FOR ICP-AES. E.D. Salin and P. Moss Department of Chemistry McGill University Montreal Quebec H3A 2K6 Canada 11:10 M3 CONTINUOUS HALOGEN GENERATION FOR ENHANCING HALIDE TRACE DETERMINATIONS BY ME' - ATOMIC EMISSION SPECTROSCOPY. Alfred0 Sanz-Medel Enrique Shchez Albert0 Menindez Francisco Camuiia Depart- ment of Physical and Analytical Chemistry Faculty of Chemistry Oviedo Spain; Carmen Quintero and Jose Cotrino Department of Applied Physics University of C6rdoba Chdoba Spain 11:30 M4 ANALYSIS OF SOILS BT FLOW INJECTION ICP-MS WITH SLURRY NEBULIZATION.Diane Beauchemin,' Maria J. Payer,' Heather E. Jamiemn and Gary W. vanloon,' Queen's University 'Department of Chemistry and 'Department of Geological Sciences Kingston Ontario K7L 3N6 Canada 1150 Discussion and Questions 1200 Lunch 2. Sample Introduction and Transport Phenomena Richard F. Browner Chairman 1:OO II3 TAILORING MICROWAVE INDUCED PLASMA DISCHARGES TO VARIOUS TYPES OF SAMPLING. J& A.C. Broekaert University of Dortmund Department of Chemistry Inorganic Chemistry P.O. Box 50 05 00 W-4600 Dortmund 50 Federal Republic of Germany 1:30 M5 EFFECTS OF ACID CONCENTRATION IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION SPEC- TROMETRY USING Mg AS A TEST ELEMENT.K. Lebas M. Marichy M. Mermet E. Poussel and J.M. Mermet Laboratoire des Sciences Analytiques University of Lyon I F-69622 Villeurbame Cedex France... JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 111 1:50 M6 NOISE CHARACTERISTICS OF AEROSOLS PRODUCED BY ICP NEBULIZERS. Shen Luan Ho-Ming Pang and RS. Houk Ames Laboratory - USDOE Department of Chemistry Iowa State University Ames IA 5001 1 210 M7 A FAST CLEARING SPRAY CHAMBER ARRANGEMENT FOR ICP-AES. G. Legere and E.D. Salin Department of Chemistry McGill University Montreal Quebec H3A 2K6 Canada 2:30 M8 DEVELOPMENT OF HIGH-SOLID-SAMPLE TORCHES FOR USN-ICP-AES. ShEKit Chan and Sidney L.Geil CETAC Technologies Inc. 5600 S. 42nd Street Omaha NE 68107 2:50 M9 A NEW MICROCONCENTRIC DIRECT NEBULIZER SYSTEM FOR INDUCTIVELY COUPLED PLASMA EMISSION SPECTROMETRY. Daniel R. Wiederin CETAC Technologies Inc. 5600 S. 42nd Street Omaha NE 68107 3 10 Break 3 9 M10 EVALUATION OF AN ULTRASONIC NEBULIZER FOR SAMPLE INTRODUCTION IN INDUCTIVELY COUPLED Jefhy M. Carey and Joseph A. Caraso Univdty of Cincimafi -t of Chemistry Cinchma& OH 45221-0172; *Envinmmcotal Health Rtsesrch and Testing Inc. 3235 Omni Dr. Cincinnati OH 45245 PLASMA ATOMIC PLASMA ATOMIC EMISSION SPECTROSCOPY (ICP-AES). T h m M. -0 W. C h d a Stary* 350 M11 APPLICATION OF THERMOSPRAY NEBULIZATION TO THE ICP ANALYSIS OF A CLASS OF HIGH DIS- SOLVED SOLIDS ENVIRONMENTAL SAMPLES. Donald R Hull and Peter k Pqisil Chanical Waste Managamat Inc.150 WtElt 137th Strctt R i v d e Il60623 and John A. Karapchak Department of Chemistry and Biochemistry Southan Illinois Univdty Carbondale IL 62901 4:lO M12 DEVELOPMENT AND CHARACTERIZATION OF A DESOLVATION SYSTEM FOR ICP-MS. Jane M. Craig J. Scott Parent and Diane Beauchemh Queen's University Department of Chemisw Kingston Ontario K7L 3N6 Canada 4:30 M13 THE HUNT FOR A SOLID SAMPLE INTRODUCTION METHOD. Eric D. Salin J.M. Ren. and L. Blain Depart- ment of Chemistry McGill University Montreal Quebec H3A 2K6 Canada 4:50 M14 DETERMINATION OF TRACES ADSORBED ON ACTIVATED CARBON BY AN ICP SLURRY TECHNIQUE. Knut D. OhLf J6rg Flock and Helmut Lmpp Hoesch Stahl AG P.O. Box'lO 50 42 W-4600 Dortmund 1 Germany 5:lO M15 SALT INDUCED MATRIX EFFECTS IN ELECTROTHERMAL VAPORIZATION PLASMA EMISSION SPEC- TROSCOPY.R4iv S. Soman and Thomas R. Gilbert Department of Chemistry and Bamett Institute for Chemical Analysis and Materials Science Northeastern University Boston MA 02115 5:30 M16 SAMPLE INTRODUCTION FOR ICPAES AND ICPMS FACT VS. FICTION. Richard F. Browner Guangxuan Zhu Vincent Nwogu and Ntombiyomusa Msimanga School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30332-0400 550 Discussion and Questions 6:OO PDl SAMPLE INTRODUCTION APPROACHES. Les Ebdon. Plymouth Analytical Chemistry Research Unit Department of Environmental Science Polytechnic South West Drakes Circus Plymouth I k o n PL4 8AA United Kingdom 7:OO EXHIBITION OPENING AND SOCIAL HOUR.Tuesday January 7,1992 8:OO PL2 DRXFI' IN ICP SPECTROCHEMISTRY ORIGJNS DIAGNOSTICS AND CORRECTION METHODS. Jean- Michel Mermet Labratoire des Sciences Analytiques Uniuksity of Lyon F-69622 Villeurbanne Cedex Franm 9:OO Break 3. Automation and Plasma Instrumentation Edward Voigtman Chairman 9:15 IL3 AUTOMATED PLASMA SPECTROCHEMISTRY. Michel Borsier BRGM B.P. 6009 F-45060 OrlCans 2 France 9:45 T1 AN AUTOMATED SYSTEM FOR ANALYSIS AND RESEARCH IN ICP-AES. George Agnes and Gary Horlick Department of Chemistry University of Alberta Edmonton Alberta T6G 2G2 Canada la05 T2 AUTOMATIC SAMPLE DILUTION WITH DATA MERGING - A NEW SOLUTION TO THE PROBLEM OFiv JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 HIGH CONCENTRATION SAMPLE ANALYSIS BY ICP.Donald R. Hull Gary W. Wiggenhauser Richard L. Hoch and Jodi L. Wojcik Chemical Waste Management. Inc. 150 West 137th Street Riverdale IL 60627; Robert Foster Thermo Jarrell-Ash 8E Forge Parkway P.O. Box 9101 Franllin MA 02038-9101 1025 T3 MOBILE INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETER SYSTEM FOR THE ANALYSIS OF HAZARDOUS WASTES. Arthur P. D'SiIva and Dan Zamzow Ames Laboratory US Department of Energy Iowa State University Ames Iowa 50011 la45 T4 FAPES - A NEW PLASMA SOURCE FOR SIMULTANEOUS MULTIELEMENT ANALYSIS. T. Hettipathirana Michael W. Blades and G. LeBlanc The University of British Columbia Department of Chemistry 2036 Main Mall Vancouver BC V6T 1Y6 Canada 11:05 T5 ANALYTICAL CHARACTERIZATION OF A FURNACE ATOMIZATION PLASMA EMISSION SOURCE INCORPORATING A NOVEL POWER SUPPLY. David J.Bir and James P. Rybarcyk Department of Chemistry CP 409T Cooper Science Ball State University Muncie IN 47306 11:Z T6 ATOMIC EMISSION SPECTROMETRY WITH USE OF A DOUGHNUT-SHAPED AND HIGH-POWER MICRO- WAVE INDUCED PLASMA SOURCE. Naoki Fur~ta The National Instimte for Environmental Studies 16-2 Onogawa Tsukuba Ibaraki 305 Japan and Masataka Koga Naka Works Hitachi Ltd. 882 Ichige Katsuta Ibaraki 305 Japan 11:45 T7 THE APPLICATION OF CHARGE-INJECTION DEVICE ARRAY DETECTION AS A DETECTOR FOR GAS CHROMATOGRAPHY. Burton R. Lamoureux Union Carbide Corporation P.O. Box 670 Bound Brook NJ 08805 and M. Bon- ner Denton University of Arizona Department of Chemistry Tucson AZ 85721 1205 Lunch 4. Artificial Intelligence Chemometrics Software for Plasma Spectrometry Eric Salin Chairman 1:OO ILA PLASMA SPECTROCHEMICAL SIMULATION WITH A GRAPHICAL USER INTERFACE PROGRAM.Edward Voigtman University of Massachusetts Department of Chemistry M a l e Graduate Research Center Amherst MA 01003-0035 1:30 T8 AN EXPERT SYSTEM FOR AUTONOMOUS INSTRUMENT OPERATION THE VIEW FROM THE TOP. Eric D. Salin V. Karanassios and D.P. Webb Department of Chemistry McGill University Montreal Quebec H3A 2K6 Canada 150 T9 ANALYSIS OF POTABLE WATERS USING ICP-MS AND PRINCIPAL COMPONENTS ANALYSIS. Dennis Yates and Rupert Aries The Perkin-Elmer Corporation 761 Main Avenue Norwalk (X 06859-0215 210 TI0 ARTIFICIAL INTELLIGENCE FOR AUTOMATED QUALITATIVE ICP-OES RIZZY THEORY AND NEU- TRAL NEURAL NETWORKS. Raher Neu&k Wolfhard Wegscheider Claudia Schierle and Matthias Otto Institute of Analyti- cal Chemistry Micro- and Radiochemistzy Graz University of Technology Technikerstrasse 4 A-8010 Graz Austria; Institute of Analytical Chemislry Bergakademie Freiber D-0 9200 Freiberg Germany 230 TI 1 IDENTIFICATION OF THE ORANGES GROWING REGION OF MICRO-NUTRIENTS ANALYZED BY ICP- AES WITH ARTIFICIAL NEURAL NETWORKS.Seifollah Nikdel Florida Department of Citrus 700 Experiment Station Road Lake Alfred Florida 33850 250 T12 OH'IMIZATION OF ACQUISITION PARAMETERS FOR ETV-ICP-MS. Robert Hutton Peter Hulmston and Jurgen Platzer VG Elemental Ion Path Road Three Winsford Cheshire CW7 3BX United Kingdom Poster Session Flow Injection Sample Introduction Automat ion Ins trumen ta tion Software Flow Injection Sample Introduction TP1 THE INFLUENCE OF MASS FLOW CONTROLLER AND ARGON GAS QUALITY OF THE DETECTION LIMIT FOR ORGANIC CARBON. Ove Emteryd Swedish University of Agricultural Sciences Department of Forest Ecology Soil Water and Plant Laboratory 901 83 Ume& Sweden TP2 NEW MEMBRANE SEPARATORS FOR PLASMA SPECTROMETRY.Akbar Montaser M. Cai S. Nam H. Liu and H. Tan George Washington University Department of Chemistry Washington DC 20052 TP3 OPTIMIZATION AND EVALUATION OF AN ULTRASONIC NEBULIZER FOR USE WITH ICP-MS. Stephen E.V JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 Long TAI 26W Martin Luther King Dr. Cincinnati OH 45219 and Theodore D. Martin EMSL USEPA 26W Martin Luther King ~ r . cinci-ti on 45268 TP4 PERFORMANCE EVALUATION OF ICP-MS WITH SAMPLE INTRODUCTION BY ULTRASONIC NEBULIZATION. Uwe Voellkopf and Petra Bmekner Bodenseewerk Perkin-Elmer GmbH Postfach 10 11 64 D-7770 h l i n g e n Geamany TPS THE LIQUID JET ULTRASONIC NEBULIZER A NOVEL SAMPLE INTRODUCTION DEVICE FOR ICPAES AND ICPMS.Matthew Tan and Richard F. Browner School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30332-0400 TP6 CHARACTERIZATION AND PERFORMANCE OF AN ULTRASONIC NEBULIZER IN ICP. Geoff Tyler Gerald Shkdnk and Deen Johnson Varian OSI 679 Springvale Rd. Mulgrave Victoria Australia and 201 Hansen Ct Wood Dale IL 60191 TP7 DETERMINATION OF METALS IN BIOLOGICAL SAMPLES USING USN-ICP-AES. Sidney L. Geil and Shi-Kit Chan CETAC Technologies Inc. 5600 S. 42nd Street Omaha NE 68107 TP8 PERFORMANCE CHARACTERISTICS OF ULTRASONIC NEBULIZATION COUPLED TO 40 MHZ ICP.I. Bren- ner Geological Survey of Israel 30 Malkhe Israel St Jerusalem 95501 Israel; P. Bremier and A. Le Marchand Jobin Yvon 16 - 18 Rue du Canal F- 91163 Lnngjumeau France TP9 ANALYSIS OF LUBRICATING OILS FOR WEAR METAIS BY ELECTROTHERMAL VAPORIZATION PLASMA EMISSION SPECTROSCOPY. Linda Aubin Rajiv S. Soman and Thomas R. Gilbert Department of Chemistry and Barnett Institute for Chemical Analysis and Materials Science Northeastern University Boston MA 021 15 TPlO FACTORS AFFECTING ANALYTICAL PERFORMANCE OF ELECTROTHERMAL VAPORIZATION SAMPLE INTRODUCTION DEVICES USED IN ICP-MASS SPECTROMETRY. Steven A. Beres and Richard D. Ediger The Perkin- Elmer Corporation 761 Main Avenue Norwalk CT 068594215 TPll SIMULTANEOUS DETERMINATION OF ARSENIC BISMUTH AND ANTIMONY IN STEEL AND NICKEL ATION (ICP-HG).E l h Akemi Osaki and Elisabeth De Oliveira Aps Villares SA. Avenida Dr. Ramos De Azevedo 133 Funda- C ~ D S.C. SUL SP CEP 09500 Brasil ALLOY BY INDUCI'IVELY COUPLED ARGON PLASMA EMISSION SPECTROMETRY WITH HYDRIDE GENER- TP12 EXTERNAL ADDITION OF INTERNAL STANDARD FOR IMPROVING PRECISION IN MULTI-ELEMENT DETERMINATION OF VOLATILE HYDRIDES BY ICP-MS. S.G. Huiden and P.G. Ek Laboratory of Analytical Chemistry Abo Akademi University Biskopsg. 8 SF-20500 Abo Finland; E. Johansson and T. Liljefors Department of Radiation Sciences Division of Physical Biology Uppsala University Box 535 S-75121 Uppsala Sweden TPl3 SIMULTANEOUS MULTI-ELEMENT SURVEY SCAN ANALYSIS OF HYDRIDE- AND NON-HYDRIDE FOR- MING ELEMENTS WITH ICP-MS USING EXPERIMENTALLY DETERMINED SAHA CORRECTION FACTORS FOR ESTIMATION OF THE ANALYTE CONCENTRATION.P.G. Ek and S.G. Hulden Laboratory of Analytical Chemistry Abo Akademi University Biskopsg. 8 SF-20500 A h Finland; E. Johansson and T. Liljefors Department of Radiation Sciences Division of Physical Biology Uppsala University Box 535 S-75121 Uppsala Sweden TP14 DIRECT POWDER INTRODUCTION - INDUCTIVELY COUPLED PLASMA EMISSION SPECTROMETRY WITH A PHOTODIODE ARRAY SPECTROMETER. Nimdasiri De SUva Mineral Resources Division Geological Survey of Canada 601 Booth St Ottawa Ontario K1A OE8 and Roger Guevremont National Research Council of Canada Institute for Environmental Chemistry Montreal Rd. Ottwawa Ontario KIA OR6 Canada TPl5 NON-METALS ANALYSIS IN ORGANIC LIQUIDS USING DIRECT SAMPLE NEBULIZATION INTO A HELIUM SURFACE WAVE PLASMA.Donald R. Hull and Peter A. Pospisii Chemical Waste Management Inc. 150 West 137th Street Riverdale IL 60623 TP16 CHARACTERISTICS OF AQUEOUS SAMPLE INTRODUCTION FOR ATMOSPHERIC AND REDUCED-PRESS- URE MICROWAVE INDUCED PLASMAS. Guangxuan Zhu and Richard F. Browner Department of Chemistry and Biochem- istry Georgia Institute of Technology Atlanta GA 30332-0400 Automation Instrumentation Sources and Software TP17 A STUDY OF DIFFERENT FORMS OF MIP-DISCHARGES OBTAINED IN A SURFATRON. Carsten Pilger Franz Leis* and Jo& A.C. Broekaert University of Dortmund Department of Chemistry Inorganic Chemistry P.O. Box 50 05 00 W-4600 Dortmuxxl50 Federal Republic of Germany; *Institut flh Spektrochemie und angewandte Spektroskopie P.O.Box 10 13 52 W-4600 Dortmund 1 Federal Republic of Germanyvi JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 TP18 CRITICAL EVALUATION AND COMPARISON OF AN ENHANCED BEENAKKER AND A STRIP LINE SOURCE MICROWAVE-INDUCED PLASMA CAVITY DESIGNS. Mark D. Argentine and Ramon M. Barnes Department of Chemistry Lederle Graduate Research Center University of Massachusetts Amherst MA 010034035 TP19 SILANE ANALYSIS WlTH A SEALED NON-FLOWING INDUCTIVELY COUPLED PLASMA. Matthias J. Jahl and Ramon M. Barnes Department of Chemistry Lederle Graduate Research Center University of Massachusetts Amherst MA 01003- 0035 T R 0 ARSINE ANALYSIS BY SEALED NON-FLOWING INDUCTIVELY COUPLED PLASMA SPECTROSCOPY.Tm- cey Jacksier and Ramon M. Bames Department of Chemistry Lederle Graduate Research Center University of Massachusetts Am- herst MA 01003-0035 TP21 A NEW ENCLOSED ICP ATOMIC EMISSION $PECTROMETER FOR RADIOACTIVE AND TOXIC MATERI- ALS. THE DESIGN AND THE PERFORMANCES. P. Marty J. Minier Ph. Guiberteau and C. Bergey C.E.A. F-21120 Is Sur Tille France; Y. Lang E. age and D. Amiaud ISA Jobin Yvon 16 rue du Canal F-91160 Longjumeau France TP22 ICPMS WITH GLOVE BOX. EXPERIENCE IN OPERATION SERVICE AND REPAIR AFI'ER 3 YEARS OF RADIOACTIVE SAMPLE ANALYSIS. Helmut Wiesmann Spectrotec GmbH W-6097 Trebur Germany; J& Ignacio Garcia Alonso and Lothar Koch Commission of the European Communities Joint Research Centre Institute for Transuranium Elements Postfach 2340 W-7500 Karlsruhe Germany TP23 AN AUTOMATED APPROACH TO ENSURE THE INTEGRITY OF THE RESULTS GENERATED BY ICP-MASS SPECTROMETRY.C. Anderau and R. Thomas Perkin Elmer Carporation 761 Main Avenue Norwalk CT 06859-0215 TP24 IMPROVED ICP-MS ANALYTICAL PRECISION USING NON-LINEAR RESPONSE DRIFI' CORRECTIONS. Micheal M. Cbeatham William F. Sangrey and William M. White Department of Geological Sciences Snee Hall Cornell Univer- sity Itha~a NY 14853-1504 TP25 PROPER USE OF CALIBRATION GRAPH IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION SPEC- TROMETRY. M. Carre and J.M. Mermet Laboratoire des Sciences Analytiques University of Lyon F-69622 Villeurbanne Cedex France TP26 FACTORIAL ANALYSIS AND RESPONSE SURFACE OF A GC-MIP SYSTEM FOR THE DETERMINATION OF HALOGENATED COMPOUNDS.Caetano S. Manuel Golding M. Rafael and Key E. Alexander Universidad Central de Veneme- la Facultad & Ciencias Escuela de Quimica. P.O. Box 47102 Caracas Venezuela TP27 TRUE OPTIMIZATION OF AN ICP SPECTROMETER. Geoff Tyler Gerald Shkolnik and Deen Johnson Varian OSI 679 Springvale Rd Mulgrave Victoria Australia and 201 Hansen CL Wood Dale IL 60191 TP28 MYERS-TRACY SIGNAL COMPENSATION IN ICP-OES FOR MINIMIZING DRIFT AND MATRIX EFFECTS. Antoaneta Krushevska R m m M. Barnes. and Laura Martines University of Massachusetts Department of Chemistry Lederle Graduate Research Center Amherst MA 01003-0035 TP29 RAPID ANALYSIS OF COMPLEX MATERIALS BY ICP-AES - APPLICATION OF ELEMENTAL TRACERS FOR RAPID ANALYSIS OF HIGH SOLID AND VISCOUS MATERIALS. I. Brenner Geological Survey of Israel 30 Malkhe Israel SL Jerusalem 95501 Israel; J.C. Gautherin A. Le Marchand and 0. Samuel Jobin Yvon 16 - 18 Rue du Canal F- 91163 Long- jumeau France TP30 OPTIMIZATION OF INTENSITY MEASUREMENT AND ACQUISITION IN MULTIELEMENT SEQUENTIAL MEASUREMENT FOR THE ANALYSIS OF COMPLEX MATERIALS. I. Brenner Geological Survey of Israel 30 Malkhe Is- rael SL Jerusalem 95501 Israel; A. Le Marchand Jobin Yvon 16 - 18 Rue du Canal F- 91163 Longjumeau France ANALYSIS BY ICP-AES - AN EVALUATION OF VARIABLE RESOLUTION AND MATHEMATICAL MODES OF 5:30 PD2 AUTOMATED PLASMA INSTRUMENTATION APPROACHES. Gerhard A. Meyer Battelle Chemical Measure- ments and Methods 7329,505 King Ave. Columbus OH 43201 7:OO Social Hour Wednesday January 8,1992 8:OO PL3 SPECTROCHEMICAL ANALYSIS SEEN AS AN INTEGRAL OF PHYSICS CHEMISTRY AND INFORMA- TION SCIENCE.Paul W. J. M. Boumans Philips Research Laboratories P.O. Box 80,000,5600 JA Eindhoven The Netherlands - 9:00 BreakJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 vii 5. Sample Preparation and Treatment for Plasma Spectroscopy Knut Ohls Chairman 9:15 IL5 MICROWAVE SAMPLE PREPARATION FOR SPECTROCHEMICAL ANALYSIS. Lois B. Jassie CEM Corp. and H.M. Kingston Center for Analytical Chemistry National Institute of Standards and Technology Gaithersburg MD 20899 9:45 IL.6 HIGH PERFORMANCE DIGESTION SYSTEMS. GUnter Knapp Department for Analytical Chemistry Micro- and Radiochemistry Graz University of Technology Technikerstrasse 4 A-8010 Graz Austria la15 W1 RAPID MICROWAVE DIGESTION PROCEDURE FOR THE DETERMINATION OF BORON IN STEELS BY MEANS OF ICP-MS.H.-M. Kuss University Duisburg Department of Analytical Chemistry htharstr. 1 D-4100 Duisburg Ger- many la35 W2 A MICROWAVE INTERRUPTED FLOW DIGESTION SYSTEM FOR ICP-AES. G. Legere V. Karanassios C. Skinner and Eric D. Salin Department of Chemistry McGill University Montreal Quebec H3A 2K6 Canada 1055 W3 A NEW PRESSURE MICROWAVE DIGESTION SYSTEM OF HIGH SECURITY AGAINST EXPLOSION. Knut D. Ohls and Horst Linn Hoesch Stahl AG P.O. Box 10 50 42 W-4600 Dortmund 1 Germany 11:15 W4 DISSOLUTION OF NON METALLIC POWDERS BY MICROWAVE OVEN IN IRON AND STEEL ANALYSIS. Maria Grazh Del Monte Tamba and Roberta Falciani Centro Sviluppo Materiali SPA Via di Caste1 Romano 100,1-00129 Roma Italy 11:35 W5 COMPARISON OF DIGESTION METHODS FOR PLASMA MASS SPECTROMETRY. Brenda S.Sheppard Cindy M. Gaston Barbara S. Barnes Karen A. Wolnik and Joseph A. Caruso National Forensic Chemistry Center US Food and Drug Administration 1141 Central Pkwy Cincinnati Ohio 45202; Department of Chemistry and Biomedical Chemistry Research Center University of Cincinnati Cincinnati OH 45221 1155 Discussion and Questions 1200 Lunch 60 Laser Assisted Plasma Spectrometry Lieselotte Moenke-Blankenburg Chairperson 1~00 IL7 LASER EXCITED ATOMIC AND MOLECULAR SPECTROSCOPY IN GRAPHITE FURNACES - MEASURE- MENT OF METALS AND NON-METALS AT THE FEMTOGRAM LEVEL. Robert G. Michel University of Connecticut De- partment of Chemistry Box U-60 Room 151 Stons CT 06269-3060 1:30 IL8 DEVELOPMENTS WITH LASER - FURNACE TECHNIQUES.Klaus Dittrich University of Leipzig Institute for Ana- lytical Chemistry Linnbtrasse 3 D-0-7010 Leipzig Federal Republic of Germany 2~00 W6 INDUSTRIAL APPLICATIONS OF LASER-INDUCED EMISSION SPECTRAL ANALYSIS (LIESA ) FOR PROCESS AND QUALITY CONTROL. Claw-Jiirgen Lorenzen and Christoph Carlhoff Krupp Forschungsinstitut GmbH Post- fach 10 22 52 D-4300 Essen 1 Federal Republic of Germany 220 W7 OFI'ICAL EMISSION SPECTROSCOPY ON LASER PRODUCED PLASMA FOR ANALYTICAL DETERMINA- TION IN SOLID SAMPLES. A. Petit A. Briand J.L Lacour and P. Mauchien DPE/SPEA/SPS CEN SACLAY F-91191 Gif Sur Yvette Cedex. France 240 W8 DESCRIPTION AND USE OF TRANSIENT SIGNALS IN LASER ABLATION - ICP - SPECTROMETRY. Lieselotte Moenke-Blankenburg Detler GUnther and J. Kammel Martin-Luther-University Institute of Analytical Chemistry Wein- berweg 16,04050 Halle Germany 3:00 W9 IMPROVEMENTS IN SPATIAL ANALYSIS BY LA-ICP-MS. Edward McCurdy and Ian Abell VG Elemental Ion Path Road Three Winsford Cheshire CW7 3BX United Kingdom Poster Session Applications Lasers Sample Preparation Standards Sample Preparation and TreatmentJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL.6 ... V l l l WP1 DECOMPOSITION OF BOTANICAL AND ACRICULTURAL FOOD PRODUCTS FOR ELEMENTAL ANALYSIS UTILZZING QUARTZ VESSELINTEGRATED COOLING TECHNOLOGY WITH OXYGEN PLASMA. Ralph Thomas White Jr. R.J. Reynolds T o b m Company Bowman Gray Technical Center Winston-Salem NC 27102 Wp2 MICROWAVE DIGESTION OF RIGID-ROD POLYMER FILMS FOR PHOSPHOROUS ANALYSIS BY INDUC- TIVELY COUPLED PLASMA ATOMIC EMISSION SPECTROMETRY.Donald W. Burns Dow USA Analytical Research Lab Western Research and Development P.O. Box 1398 Pittsburg CA 94565 IN BIOLOGICAL SAMPLES. Antoaneta Krushevska Ramon M. Barnes Chitra Amarasbiwaradena Henry Foner and Laura Martjnes University of Massachusetts Department of Chemistry Lederle Graduate Research Center Amherst MA 01003-0035 Wp3 COMPARISON OF SAMPLE DECOMPOSITION PROCEDURES FOR THE ICP-AES DETERMINATION OF ZINC WP4 SURVEY OF DECOMPOSITION TECHNIQUES FOR MULTIELEMENT ICP ANALYSIS USING MULTIVARI- ABLE STATISTICS. I. Brenner Geological Survey of Israel 30 Malkhe Israel St. Jerusalem 95501 Israel; M Borsier Bureau Recherches Geologiques et Miniexes (BRGM) Orleans France WP5 PREPARATION OF OIL SAMPLES PRIOR TO ANALYSIS BY USN-ICP-AES.Shi-Kit Chan and Sidney L. Geil CETAC Technologies Inc. 5600 S. 42nd Street Omaha NE 68107 WP6 DIRECT MULTIELEMENT ANALYSIS OF ADVANCED MATERIALS USING A MINI SPRAY DRIER INTER- FACED TO A SIMULTANEOUS ICP-AES. Gerhard A. Meyer Battelle Chemical Measurements and Methods 7329,505 King Ave. Columbus OH 43201 WW APPLICATION OF INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY TO AN ACID MINE DRAIN- AGE CONTAMINATION STUDY USING ON-LINE CHELATION CONCENTRATION CHROMATOGRAPHY. Lynda M. Faires and Charles J. Patton US Geological Survey 5293B Ward Road Arvada CO 80002 Wps DETERMINATION OF AS AND Se IN DRINKING WATER USING ON-LINE ION EXCHANGE PRECONCENTRA- TION WITH ICAP-AES. Ronald Manabe John Riviello and Archava Siriraks Thermo Jamell Ash 175 Jefferson Dr.Menlo Park CA 94025; Dionex Corp. 1228 Titan Way Sunnyvale CA 94088 Wp9 MINIMIZATION OF CHLORIDE MATRIX INTERFERENCES VIA ON-LINE ION EXCHANGE INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY. John T. Creed Theodore D. Martin US EPA 26 W. Martin Luther King Drive Cincinnati OH 45268 and Steve E. h g Technology Applications Inc. 26 W. Martin Luther King Dr. Cincinnati Ohio 45268 WP10 ELIMINATION OF MATRIX AND OXIDE INTERFERENCES IN DETERMINATION OF PLATINUM GROUP TION. Mohammad B. Shabani and Akimasa Mas& Department of Chemistry Faculty of Science The University of Tokyo Hongo Tokyo 113 Japan ELEMENTS BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY USING ON-LINE PRECONCENTRA- WP11 DETERMINATION OF TECHNETIUM49 BY ICP-MS WITH ON-LINE SAMPLE PRECONCENTRATION.DOU- glas T. Heitkemper Brenda S. Sheppard Cindy Gaston and Karen A. Wolnik National Forensic Chemistry Center US Food and Drug Administration 1141 Central Parkway Cincinnati OH 45202; Lihseuh Chang Edward R. Deutsch and Joseph A. Caruso Department of Chemistry and Biomedical Chemisq Research Center University of Cincinnati Cincinnati OH 45221 WP12 TECHNIQUES OF ON-LINE PRECONCENTRATION FOR ICP-ATOMIC EMISSION SPECTROMETRY. Sodin La Department of Applied Chemistry China University of Geosciences Wuhan 430074 People's Republic of China WP13 OFF-LINE AND ONLINE PRECONCENTRATION TECHNIQUES FOR DETERMINATION OF BISMUTH IN SEAWATER BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY. Mohammad B. Shabani and Akimasa Masuda Department of Chemistry Faculty of Science The University of Tokyo Hongo Tokyo 113 Japan WP14 SEA WATER ANALYSIS BY ICP-AES GFAAS AND ICP-MS. Jin-Yi Pemg and Shu-Hua Chen China Steel Corp.Steel and Aluminum R and D Department Lin Hai Industrial District P.O. Box 47-29 Hsim Kang Kaohsiung 81233 Taiwan Republic of China WP15 DETERMINATION OF PHOSPHOROUS IN COPPER ALLOYS USING ICP-AES USING ELECTRICALLY DIS- PERSED SAMPLES. EUas Eljuri Miguel Murillo and Alberto Ferniindez Centro de Quimica Analitica Facultad de Ciencias Es- cuela de Quimica Universidad Central de Venezuela P.O. Box 47102 Caracas 1041-A Venezuela WP16 STUDIES ON SPARK ELUTRIATION FOR THE DISSOLUTION OF METALLIC SAMPLES. Holger Alexi and Jc& A.C. Broekaert University of Dortmund. Department of chemistry horganic Chmistq P.O.Box 50 05 00 W-4600 Dortmund 50 Federal Republic of Germmy WP17 THE DETERMINATION OF ULTRA-TRACE PGE CONCENTRATIONS IN ROCK PULPS BY HIGH TEMPERA- TURE DRY CHLORINATION FOLLOWED BY ICP-MS ANALYSIS A POTENTIAL ALTERNATIVE TO NIS FIREJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 ix ASSAY. BJ. Perry and J.C. Van Loon Department of Geology University of Toronto Toronto Ontario M5S 3B1 and D.V. Speller INCO Ltd. J. Roy Gordon Research Laboratoxy Toronto Ontario Canada Laser Assisted Plasma Spectrometry WP18 NEW APPROACHES TO LASER ABLATION SAMPLE INTRODUCTION SYSTEMS FOR INDUCTIVELY COUPLED PLASMA SPECTROMETRY. X.R. Liu and Gary Horlick Department of Chemistry University of Alberta Edmonton Alberta T6G 2G2 Canada WP19 TOWARDS THE QUANTITATIVE ANALYSIS OF ROCK SPECIMENS USING TRA-LA-ICP-MS. Micheal M.Chea- tham William F. Sangrey and William M. White Departmat of Geological Sciences Snee Hall Cornell University Ithaca NY 14853-1504 WP20 STUDlES ON MATRIX EFFECTS OF LASER SAMPLING ICP-ATOMIC EMISSION SPECTROMETRY. Soulin Lin Department of Applied Chemistry China University of Geosciences Wuhan 430074 People’s Republic of China WP21 ANALYSIS OF PEROVSKITE-TYPE CERAMIC MATERIALS BY MEANS OF ICP-AES AND LA-ICP-AES. Detla Gthther Lieselotte Moenke-Blankenburg Martin-Luther-University Institute of Analytical Chemistry Weinbenveg 16,04050 Halle Germany; Hubertus Nickel and Werner Fischer Research Center JUlich Institute of Reactor Materials P.O. Box 1913 W-5170 Jiilich 1 Germany Applications WP22 DETERMINATION OF TRACE METALLIC IMPURITIES IN SPECIAL STEELS BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION (ICP/AES).Rosa Ana Conti and Luiz Rinaldo Bizaio Fundapo de Tecnologia Industrial Centro de Materiais Refratarios Cx. Postal 16 Lorema (SP) CEP 12600 Brasil WP23 DETERMINATION OF COMPOSITION AND TRACE METALLIC IMPURITIES IN NIOBIUM-BASED ALLOYS BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION SPECTROMETRY (ICPIAES). Rosa Ana Conti and Luiz Rinaldo Bizaio Fundqm de Tecnologia Industrial Centm de Materiais Refiatarios Cx. Postal 16 Lorena (SP) CEP 12600 Brad WP24 OPTIMIZED WAVELENGTHS FOR ANALYSIS OF NEODYMIUM-IRON ALLOYS BY ICP. Mark L. Tobias Neomet Corp. Route 168 P.O. Box 325 West Pittsburg PA 16160 WP25 DETERMINATION OF TRACE LEVELS OF BORON IN STEEL FASTENERS BY ICP-AES USING METHYL BORATE DISTILLATION.Robert S. Schwartz US Customs Service Washington DC 20229 WP26 INDIRECT DETERMINATION OF PHYTIC ACID IN FOODS BY ICP-AES. Jorma Kumpulainen Central Laboratory Agricultural Research Centre of Finland 31600 Jokioinen Finland 530 PD3 NOVEL SAMPLE PREPARATION APPROACHES. Mark Tatro Spectra P.O. Box 352 Pompton Lakes NJ 07442 7:OO Social Hour Thursday January 9,1992 7. Excitation Mechanisms and Plasma Phenomena John Olesik Chairman 8:OO PLA FUNDAMENTAL STUDIES OF THE INDUCTIVELY COUPLED PLASMA - PROGRESS AND PROBLEMS. Michael W. Blades The University of British Columbia Department of Chemistry 2036 Main Mall Vancouver BC V6T 1Y6 Canada 9:OO Break 9:15 IL9 FUNDAMENTAL STUDIES OF SURFACE WAVE INDUCED PLASMAS. Joseph Hubert Universit6 de Montreal D6pamment de chimie P.O.Box 6128 Station A Montnkl Quebec H3C 3J7 Canada 9:45 Thl THE APPLICATION OF A FOURIER TRANSFORM SPECTROMETER SYSTEM TO THE FUNDAMENTAL CHARACTERIZATION OF ANALYTICAL EMISSION SOURCES. Gary Horlick T.B. Wang G. Fulton and Y. Zhao Depart- ment of chemistry University of Alberta Edmonton Alberta T6G 2G2 CanadaX JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 1005 Th2 INFLUENCE OF INDIVIDUAL DROPLETS AND VAPORIZING ANALYTE PARTICLES ON PLASMA EXCI- TATION AND IONIZATION PROCESSES. John W. Oledk and Steven E. Hobbs Department of Chemistry Venable and Kenan Laboratories University of North Carolina Chapel Hill NC 27599-3290 1025 Th3 A PARAMETRIC STUDY OF ORGANIC SOLVENT SAMPLE INTRODUCTION ON ICP FUNDAMENTAL PROPERTIES.M.W. Blades and D. Weir The University of British Columbia Department of Chemistry 2036 Main Mall Vancouver BC V6T 1Y6 Canada la45 Th4 KINETICS OF CHARGE TRANSFER BETWEEN MAGNESIUM AND ARGON IN THE INDUCTIVELY COUPLED PLASMA. Paul B. Famswarth Department of Chemistry Brigham Young University Provo UT 84602 and Nicolo Omenetto Joint Research Centre Environmental Institute Ispra Establishment 1-21020 Ispra (Varese) Italy 11:05 Th5 IS THE ICP "BULLET" A USEFUL SPATIAL REFERENCE? Paul A. Galley and Gary M. Hieftje Indiana University Department of Chemistry Bloomington IN 47405 11:25 Th6 TEMPERATURE MEASUREMENTS OF INDUCTIVELY COUPLED PLASMA A COMPARISON OF Nz+ ROTATIONAL SPECTRA AND OPTICAL PYROMETRY. Isam Marawi Bradley A. Bielsky Frank R. Meeks and Joseph A. Caruso Department of Chemistry ML 172 University of Cincinnati Cincinnati Ohio 45221 11:45 Th7 RECENT INVESTIGATIONS INTO THE "EIE INTERFERENCE".Paul A. Galley David Hanselman Norman Sesi Min Wu and Gary M. Hieftje Indiana University Department of Chemistry Bloomington IN 47405 1205 Lunch 1:OO Th8 SIGNAL ENHANCEMENT WITH ADDED HYDROGEN IN ELECTROTHERMAL VAPORIZATION INDUC- TIVELY COUPLED PLASMA ATOMIC EMISSION SPECTROMETRY. J. Matousek and J.M. Mermet Laboratoire des Sciences Analytiques University of Lyon I F-69622 Villeurbame Cedex France 1 :20 Th9 VAPORIZATION PROCESSES OF CARBIDE-FORMING ELEMENTS IN ELECTROTHERMAL VAPORIZA- TION ICP-MASS SPECTROMETRY. Richard D. Ediger Perkin-Elmer Corporation 761 Main Avenue Norwalk CT 06859-0215 8. Spectroscopic Standards Reference Materials and Characterization H.M.Kingston Chairman 1:40 ILlO ROLE OF ICP-AES FOR REFERENCE VALUES IN BIOLOGICAL MATRICES. S. Caroli Istituto Superiore di Saniti Vide Regina Elena 299,I-00161 Rome Italy 210 ILll ULTRATRACE CHARACTERIZATION OF BULK REFRACTORY METALS. Hugo M. Ortner Technical Hoch- schule Darmstadt Materialwissenschaft. Fachgebeit Chemische Analytik Petersenstrasse 21 D-6100 Darmstadt Germany 240 ThlO PURIFICATION OF HIGH PURITY MATERIALS FOR THE PREPARATION OF ICP/DCP STANDARDS. Warren Miller and Phillip Blacher MV Laboratories P.O. Box 370 Three Bridges NJ 08887 Poster Session Plasma Sources Mass Spectrometry Chromatographic Detectors Plasma Sources ThPl A METHOD FOR INVESTIGATING THE DOMINANT ELECTRON-LOSS MECHANISMS IN LOW TEMPERA- TURE PLASMAS. George P.Miller Chemistry Department University of Alabama in Huntsville Huntsville AL 35899 ThP2 SPECTROMETRY AND CHARACTERIZATION OF ORGANIC COMPOUNDS BY MEANS OF LOW-PRESSURE LOW-POWER MICROWAVE INDUCED PLASMA (MIP). H.-M. Kuss Department of Analytical Chemistry University Duisburg Lotharstr. 1 D-4100 Duisburg Germany ThP3 ANALYTE ATOMIZATION AND EXClTATION IN FAPES STUDIED USING TEMPORAL AND SPATIAL EMISSION BEHAVIOR. T. Hettipathirana and M.W. Blades Department of Chemistry The University of British Columbia 2036 Main Mall Vancouver BC VtZ 1Y6 Canada ThP4 HOLLOW ANODE - FURNACE ATOMIZATION NON-THERMAL ATOMIZATION SPECTROMETRY. Philip G. Riby and James Hardy U.S. Department of Agriculture Beltsville Human Nutrition Research Center Bldg. 161 BARC-East Beltsville MD 20705JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1.VOL. 6 xi Plasma Source Mass Spectrometry ThP5 ICP-MS ANALYSIS OF SUB-MILLIGRAM SAMPLES OF GEOLOGICAL MATERIALS USING A RECYLCING NEBULIZATION SYSTEM WITH A DISPOSABLE SPRAY CHAMBER. Zhongxing Chen Henry P. Longerich and Brian J. Fryer Department of Earth Sciences and Centre for Earth Resources Research Memorial University of Newfoundland St. John's NF A1B 3x5 Canada ThP6 DESIGN AND OIWMIZATION OF A VERSATILE SAMPLE INTRODUCTION INTERFACE FOR ICP-MS. Gregory R. Peters and Diane Beauchemin Queen's University Department of Chemistry Kingston Ontario Canada K7L 3N6 ThP7 I"SIC/EXTRINSIC BORON-10 IN MALE LONG EVANS RATS. Richard A. Vanderpool and Phyllis E. Johnson USDA-ARS Grand Forks Human Nutrition Research Center Grand Forks ND 58202 TbPS INTERFERENCES OF MATRIX ELEMENTS ON THE TRACE ELEMENT DETERMINATION IN STEELS BY ICP-MS.H.-M. Kuss Department of Analytical Chemistry University Duisburg htharstr. 1 D-4100 Duisburg Germany ThP9 APPLICATION OF ICP-MS TO THE ANALYSIS OF PHOTOGRAPHIC MATERIALS. Uwe Voellkopf and Michael Paul Bodenseewerk Perkin-Elmer GmbH Postfach 10 11 64 D-7770 oberlingen Germany ThPlO ICPMS BACK TO THE FUTURE PART 1. David W. Koppenaal Pacific Northwest Laboratory P.O. Box 999 MS P8-08 Richmond WA 99352 ThPll APPLICATION OF ATOMIC MASS SPECTROMETRY (ICPMS) TO AGRICULTURE. Milan h a t Donald S. Gamble and Glen F.R. Gilchrist Land Resource Research Centre Agriculture Canada Ottawa Ontario K1A OC6 Canada ThP12 ULTRATRACE ANALYSIS OF U AND Th IN ULSI MATERIALS BY ETV-ICP-MS.Hideki Matsunaga Materials Application Department. Toshiba R&D Center 1 Komukai Toshibacho Saiwai-ku Kawasaki-shi Kanagawa-ken 210 Japan ThP13 DATA ACQUISITION AND EVALUATION BY A COMPUTER-CONTROLLED LANGMUIR PROBE SYSTEM. Jeffrey M. Weston Ronald R. Williams and R. Kenneth Marcus Department of Chemistry Howard L. Hunter Chemical Labora- tories Clemson University Clemson SC 29634-1905 ThPl4 EFFECTS OF SUPPORT GAS FLOW ON THE EMISSION CHARACTERISTICS OF AN RF GLOW DISCHARGE ATOMIC EMISSION SOURCE. Chris Lazik and R. Kenneth Marcus Department of Chemistry Howard L. Hunter Chemical Laboratories Clemson University Clemson SC 29634-1905 ThP15 ROLE OF ANODE GEOMETRY ON RF GLOW DISCHARGE MASS SPECTROMETRY. Paula R.Cable and R. Kenneth Marcus Department of Chemistry Howard L. Hunter Chemical Laboratories Clemson University Clemson SC 29634 ThP16 TWO-DIMENSIONAL DIFFUSION IN A GLOW DISCHARGE CELL THE EFFECT OF CELL GEOMETRY ON ANALYTICAL PERFORMANCE. Mark van Straaten Akos Vertes and Renaat Gijbels University of Antwerp Department of Chemistry Universiteitplein 1 B-2610 WilrijWAntwerp Belgium ThP17 OPTIMIZATION OF AQUISITION AND INTENSITY MEASUREMENT FOR ION SOURCE OF GDMS. H.B. Lim Composition Analysis Laboratory Korea Standards Research Institute P.O. Box 3 Taedok Science Town Taejon 305-606 Republic of Korea ThP18 ANALYTICAL AND SPECTRAL CHARACTERISTICS OF GD-MS. Gary Horlick L. Burton and X. Feng Depart- ment of Chemistry University of Alberta Edmonton Alberta T6G 2G2 Canada ThP19 QUADROPOLE VERSUS MAGNETIC SECTOR GDMS COMPARISON OF QUANTITATIVE ANALYTICAL CA- PABILITIES.Wojciech Vieth Angelika Raith and Jack C. Huneke 301 Chesapeake Dr. Redwood City CA 94063 ThP20 ANALYSIS OF HIGH P'JRITY TITANIUM AND TITANIUM ALLOYS BY GLOW DISCHARGE MASS SPECTROMETRY. Duencheng Fang Materials Research COT. Route 303 Orangeburg NY 10962 Chromatographic Detectors ThP21 APPLICATION OF A MICROWAVE INDUCED PLASMA ATOMIC EMISSION DETECTOR FOR GC TO QUANTITATION OF HALOGENATED COMPOUNDS. Nada Kovacic and Terry L. Ramus Dow Chemical Company P.O. Box 1398 Pittsburg CA 94565 ThP22 DETERMINATION OF VOLATILE HALOGENATED HYDROCARBONS IN PUBLIC INDOOR SWIMMING POOL AIR WITH CC-AED-DETECTION Michael Faust Frank Winter and Karl Cammann Institut fiir Chemo- und Biosen- sor& e.V.c/o Lehrstuhl ffir Analytische Chemie Wilhelm-Klemm Strasse 8 D-4400 Munster Federal Republic of Germanyxii JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 ThP23 ANALYSIS OF PESTICIDE MIXTURES BY SUPERCRITICAL FLUID CHROMATOGRAPHY - MICROWAVE- INDUCED PLASMA MASS SPECTROMETRY. Lisa K. Olson and Joseph A. Caruso University of Cincinnati Department of Chemistry ML 172 Cincinnati OH 45221 ThP24 INDUCTmLY COUPLED PLASMA MASS SPECTROMETRY AS DETECTOR FOR CHROMATOGRAPHY. Chunliang Bi E. Hywel Evans and Joseph A. Caruso University of Cincinnati Department of Chemistry Cincinnati OH 45221- 0172 7:00 conference Dinner Friday January 10,1992 9. Plasma Source Mass Spectrometry Fundamentals James McLaren Chairman 8:OO PL5 A COMPARISON OF ICP-AES AND ICP-MS FOR ELEMENTAL ANALYSIS.Gary Horlick University of Alberta Department of Chemistry Edmanton Alberta T6G 2G2 Canada 9:OO Break 9:15 IL12 WHAT’S REALLY NEW IN ICP-MS? RS. Houk H.S. Niu X. Chen A.R. Warren and L. Alves Ames Laboratory - USDOE Department of Chemistry Iowa State University Ames IA 5001 1 9:45 IL13 CONVERTABLE ICP AND GD MASS SPECTROMETER. Hiroshi Kawaguchi Nagoya University Faculty of Engin- eering Chikusa-ku Nagoya 464 Japan la15 F1 SPACE CHARGE MODIFICATION OF MEASURED ION KINETIC ENERGIES IN ICP-MS. Scott D. Tanner SCIEX 55 Glenmeron Road Thornhill Ontario L3T 1P2 Canada 1&35 F2 SIGNAL FLUCTUATIONS IN INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY. Steven E. Hobbs and John W. Olesk Department of Chemistry Venable and Kenan Laboratories University of North Carolina Chapel Hill NC 27599-3290 1055 F3 MORE ICP-MS POLYATOMIC ION INTERFERENCES AND PROGRESS IN UNDERSTANDING OF CON- COMITANT ION MATRIX SUPPRESSION AND ENHANCEMENT EFFECTS.Henry P. Longerich Simon E. Jackson and Brian J. Fryer Department of Earth Sciences and Centre for Earth Resources Research Memorial University of Newfoundland St. John’s NF A1B 3x5 Canada 11:15 F4 STUDIES OF SURFACE WAVE PLASMAS AS ION SOURCES IN MASS SPECTROMETRY. Denis Boudreau and Joseph Hubert D6partement de chimie Universit6 de Man&&& P.O. Box 6128 Station A MontrM Qui%ec H3C 3J7 Canada 11:35 F5 DESIGN PARAMETERS OF A NEW ICP-MS INSTRUMENT. Chris Tye and Peter Hitchen VG Elemental Ion Path Road Three Winsford Cheshire CW7 3BX United Kingdom 1155 Discussion and Questions 1200 Lunch 10.Plasma Source Mass Spectrometry Applications Sam Houk Chairman 1:OO IL14 APPLICATIONS OF ICP-MS IN ENVIRONMENTAL ANALYTICAL CHEMISTRY. James W. McLaren National Research Council of Canada Institute for Environmental Chemistry Ottawa Ontario K1A OR6 Canada 1:30 F6 CHEMICAL CHARACTERIZATION OF SUBMISSION SUSPENDED PARTICULATES BY FIELD FLOW FRACTIONATION - INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY. Howard E. Taylor and John R. Gar- barino US Geological Survey Denver Colorado; Deirdre Hotchin and Ronald Beckett Water Studies Centre and Department of Chemistry Monash University Melbourne Australia 150 F7 MULTIELEMENTAL ANALYSIS OF ENVIRONMENTAL SAMPLES WITH LOW-COST INDUCTIVELY COUPLED PLASMA MASS SPECTROMETER. Michael R.Pianb and Jeffrey A. Holmgren WMI Environmental MonitoringJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 199 1 VOL. 6 ... X l l l Laboratories Inc. 2100 Cleanwater Drive Geneva IL 60134 2:lO F8 ARSENIC SPECIATION IN BIOLOGICAL AND ENVIRONMENTAL SAMPLES BY LIQUID CHROMATO- GRAPHY COMBINED WITH ON-LINE HYDRIDE GENERATION AND INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY. Raimund Roehl and Maricia M. Alforque California Public Health Foundation Department of Health Services Hazardous Materials Laboratory 2151 Berkeley Way Berkeley CA 94704 and John Riviello. Dionex Corporation 1228 Titan Way Sunnyvale CA 94088-3606 2:30 F9 ICPMS FOR PLANT ANALYSIS. Greg W. Johnson and Robert 0. Miller DANR Analytical Lab and Patrick H. Brown Department of Pomology University of Califomia Davis California 95616 250 F1O DETERMINATION OF ORGANOMETALLIC COMPOUNDS BY SUPERCRITICAL FLUID CHROMATO- GRAPHY-INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY (SFC-ICP-MS).Jeffrey M. Carey Nohora P. Vela and Joseph A. Caruso University of Cincinatti Department of Chemistry Cincinnati OH 45221-0172 3:lO Break 3:30 F11 THE ANALYSIS OF REACTIVE ORGANOMETALLIC SPECIES IN VOLATILE ORGANICS BY INDUCTIVE- LY COUPLED PLASMA-MASS SPECTROMETRY. James Hartley Steve J. Hill and Les Ebdon Plymouth Analytical Chem- istry Research Unit Department of Environmental Science Polytechnic South West Drakes Circus Plymouth Devon PLA 8AA. United Kingdom 350 F12 EXPERIENCE IN THE ANALYSIS OF ACTINIDES IN NUCLEAR MATERIALS BY ICPNS. Jo& Ignacio Garcia Alonso Dominique Thoby-Schultzendorff Bruno Giovannone and Lothar Koch Commission of the European Communities Joint Research Centre Institute for Transuranium Elements Postfach 2340 D-7500 Karlsruhe Germany 4:lO F13 THE EFFECT OF MAJOR AND MINOR ELEMENTS ON THE ESTIMATION OF THORIUM AND URANIUM IN ROCK SAMPLES BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY.V. Balaram K.V. Anjaiah and C. Manikyamba National Geophysical Research Institute Hyderabad-500 007 India 4130 F14 LASER ABLATION MICROPROBE-INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY (LAM-ICP- MS). Simon E. Jackson Henry P. Longerich and Brian J. Fryer Memorial University of Newfoundland Department of Earth Sciences and Centre for Earth Resources Research St. John's NF A1B 3x5 Canada 4:50 F15 ANALYSIS OF USGS ROCK STANDARDS BY LASER ABLATION INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY.Ruth E. Wolf Environmental Chemistry Unit EG&G Idaho Tnc. P.O. Box 1625 Idaho Falls ID 83415-4107 5:lO F16 ANALYSIS OF SOLID SAMPLES BY LASER ABLATION HIGH RESOLUTION ICP-MS. Amanda Walsh Neil Bradshaw and Ian Abell VG Elemental Ion Path Road Three Winsford Cheshire CW7 3BX United Kingdom 5130 F17 DETERMINATION OF TRACE ELEMENTS IN POLYMERS BY LASER ABLATION - INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY. Charles J. Lord III and Eric W. Nelson Phillips Petroleum Company Research and Development Bartlesville OK 74004 550 Discussion and Questions 6:OO PD4 CRITICAL NEEDS FOR PLASMA SOURCE MASS SPECTROMETRY Akbar Montaser George Washington University Department of Chemistry Washington DC 20052 7:OO Social Hour Saturday January 11,1992 8:OO P M TOWARD THE NEXT GENERATION OF PLASMA-SOURCE MASS SPECTROMETERS.Gary M. Hieftje Indiana University Department of Chemistry Bloomington IN 47405 9:OO Break 11. Glow Discharge Spectrometry Sergio Caroli and Kenneth Marcus Chairmen 9:15 IL15 GLOW DISCHARGES FOR PLASMA SPECTROCHEMISTRY. Willard W. Harrison University of Florida 2014 Turlington Hall Gainesville FL 3261 1xiv JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 9:45 S1 SOME ASPECTS ON LINE SELECTION FOR QUANTITATIVE DEPTH PROFILE ANALYSIS WITH GD-OES. Arne Bengtson Swedish Institute for Metals Research Drottning lKristinas viig 48 S-11428 Stockholm Sweden 1&05 S2 LINE SELECTION AND ANALYTICAL FIGURES OF MERIT IN RADIO FREQUENCY GLOW DISCHARGE EMISSION SPECTROMETRY. Tina Harville and R.Kenneth Marcus Department of Chemistry Howard L. Hunter Chemical Laboratories Clemson University Cleanson SC 29634-1905 1025 S3 SAMPLING RADIO FREQUENCY GLOW DISCHARGE SOURCES WITH ION TRAP AND FOURIER TRANS- FORM/ION CYCLOTRON RESONANCE MASS SPECTROMETERS. R. Kenneth Marcus' Douglas C. Duckworth'q Gary L. Glish2 Scott A. McLuckey2 Michelle Buchanan2 Marcus B. Wise2 Joseph M. Pochkowski3 and Robert R. Weller3; 'Department of Chemistry Howard L. Hunter Chemical Laboratories Clemson University Clemson SC 29634-1905; 2Analytical Chemistry Division Oak Ridge National Laboratory Oak Ridge TN 37831; h v h m e n t a l Technology Section Savannah River Laboratory Aiken SC 29802 1045 S4 A RADIO-FREQUENCY GLOW DISCHARGE SOURCE FOR MASS SPECTROMETRY.Jeffrey J. Giglio E. Hywel Evans and Joseph A. Caruso University of Cincinnati Department of Chemistry Cincinnati OH 45221-172 11:05 S5 IN-DEPTH ANALYSIS OF SURFACE LAYERS BY GLOW DISCHARGE MASS SPECTROMETRY. Norbert Jakubowski and Dietmar Stuewer Institut flir Spektrochemie und angewandte Spektroskopie Bunsen-Kirchhoff-Str. 11 D-W 4600 1 Federal Republic of Germany 1125 S6 DEPTH PROFILING BY GLOW DISCHARGE MASS SPECTROMETRY. Dyfvdd Milton Robert Hutton Neil Bradshaw Mark Jackson and Angelica Raith VG Elemental Ion Path Road Three Winsford Cheshire CW7 3BX United Kingdom 11:45 S7 QUANTITATIVE DEPTH PROFILING OF CYLINDRICAL AND PLANAR LAYERED SAMPLES WITH GDMS. Mark van Straaten and Renaat Gijkls University of Antwerp Department of Chemistry Universiteitsplein 1 B-2610 WilrijWAnt- werp Belgium 1205 Lunch 12.Plasma Spectroscopic Detection in Chromatography Peter Uden Chairman 1:OO IL16 INDUCTIVELY COUPLED PLASMA DETECTION IN MICROCOLUMN CHROMATOGRAPHY. Kiyokatsu Jinno Toyohashi University of Technology Materials Science Tempakucho Toyohashi 440 Japan 1:30 S8 APPLICATION OF GC-ESD IN ENVIRONMENTAL ANALYSIS. Giinter Knapp B. Platzer E. Leitner R. Gross and A. Schalk Graz University of Technology Department for Analytical Chemistry Micro- and Radiochemistry Technikerstrasse 4 A-8010 Graz Austria 150 S9 DETERMINATION OF OXYGEN-CONTAINING ADDITIVES IN GASOLINE BY GAS CHROMATOGRAPHY WITH A MICROWAVE-INDUCED PLASMA EMISSION DETECTOR. Scott R. Goode and Christopher L. Thomas Depart- ment of Chemistry University of South Carolina Columbia SC 29208 210 S10 ULTRATRACE SPECIATION OF ORGANOMETALLIC COMPOUNDS BY GAS CHROMATOGRAPHY ATOMIC EMISSION SPECTROMETRY.Ryszard Lobinski and Freddie C. A h University of Antwerp Department of Chemistry Universiteitsplein 1 B-2610 Wilrijl Belgium. 230 S11 ELEMENT SPECIFIC DETECTION IN GC BY MICROWAVE INDUCED PLASMA ATOMIC EMISSION SPECTROMETRY USING A SURFATRON AND A NIR FI' SPECTROMETER SUMMARY OF DEVELOPMENTS AND PERFORMANCE. Robert L.A. Sing Claude Lauzon Khan Chi Tran and Joseph Hubert UniversiG de MontrCal D6partement de Chimie P.O. Box 6128 Station A Montrkal Qukbec H3C 3J7 Canada 250 S12 PYROLYSIS-GC-AES OF SEDIMENTS COALS AND OTHER PETROCHEMICAL PRECURSORS. Peter C. Uden Jeffrey A. Seeley and Yadi Zeng Department of Chemistry Lederle Graduate Research Tower A University of Massachu- setts Amherst MA 01003 and Timothy I.Eglinton Woods Hole Oceanographic Institute Woods Hole MA 02543 3 10 Break 3:s S13 A MICROCONCENTRIC DIRECT NEBULIZER FOR INTERFACING MICROCOLUMN ION EXCHANGE CHROMATOGRAPHY WITH AN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION SPECTROMETER FOR ELEMENTAL SPECIATION. Daniel R. Wiederin CETAC Technologies Inc. 5600 S. 42nd Street Omaha NE 68107 and Douglas T. Gjerde Smasep Inc. 1600 Wyatt Drive Suite 10 Santa Clara CA 95054JOURN.4L OF ANALYTIC.4L ATOMIC SPECTROMETRY. AUGUST 199 1. VOL. 6 XV 3~45 S14 ELEMENTAL SPECIATION BY LC-ICP-MS WITH DIRECT INJECTION NEBULIZATION. S.-C. Chum R. Nedderson and R.S. Houk Ames Laboratory - USDOE Department of Chemistry Iowa State University Ames IA 5001 1 4:05 S15 A THERMOSPRAY-MEMBRANE SEPARATOR INTERFACE FOR PORPHYRIN SPECIATIOS STUDIES IN CRUDE OILS BY HPLC-ICP-MS. Ron J.Lukasiewicz and B.D. Webb Unocal Science and Technology Division Unocal Corpor- ation 376 South Valencia Ave. Brea CA 92621 4125 S16 SEPARATION OF METALLOPORPHYRINS BY LIQUID CHROMATOGRAPHY AND DETECTION BY IS- DUCTIVELY COUPLED PLASMA MASS SPECTROMETRY. Uma T. Kumar E. Hywei Evans John G . Dorsey and Joseph A. Caruso Department of Chemistry University of Cincinnati Cincinnati OH 45221-0172 4:45 S17 EFFECTS OF TEMPERATURE PRESSURE PROGRAMMING AND MOBILE PHASE COMPOSITION IN SUPERCRITICAL FLUID CHROMATOGRAPHY (SFC) FOR THE SEPARATION OF ORGAYOTIN COMPOUXDS USING ICP-MS DETECTION. Nohora P. Vela Hywel Evans and Joseph A.Caruso Department of Chemistry University of Cincinnati Cincinnati OH 45221 -0172 5 9 5 PD5 CRITICAL NEEDS FOR PLASMA SOURCE CHROMATOGRAPHIC DETECTION SYSTEMS. Joesph A. Caruso Department of Chemistry University of Cincinnati Cincinnati OH 45221 -0172 6:OO CONFERENCE CLOSING.xvi JOURNAL OF AN.ALYTICAL ATOMIC SPECTROMETRY AUGUST 1991 VOL. 6 Ramon #A. Barnes Editor Department of Chemistry GRC Towers University of Massachusetts Amherst MA 01 003-0035 Telephone (41 3) 545-2294 fax 545-4490 0 bjective The ICP lNFORMA TlON NEWSLETTER is a monthly journal published by the Plasma Research Group at the University of Massachusetts and is devoted exclusively to the rapid and impartial dissemination of news and literature information re- lated to the development and applications of plasma sources for spectrochernical analysis.Background ICP stands for inductively coupled plasma discharge which during the past decade has become the leading spectrochemi- cal excitation source for atomic emission spectroscopy. ICP sources also are applied commercially as an ion source for mass spectrometry and as an atom and ion cell in atomic fluorescence spectrometry. The popularity of this source and the need to collect in a single literature reference all of the pertinent data on ICP stimulated the publication of the ICP INFORMA TlON NEWSLETTER in 1975. Other popular plasma sources i.e. microwave induced plasmas direct current plas- mas and glow discharges also are included in the scope of the ICP lNFORMA TlON NEWSLETTER. Scope As the only authoritative monthly journal of its type the ICP lNFORMATlON NEWSLETTER is read in more than 40 coun- tries by scientists actively applying or planning to use the ICP or other types of plasma spectroscopy.For the novice in the field the ICP lNFORMATlON NEWSLETTER provides a concise and systematic source of information and background material needed for the selection of instrumentation or the development of methodology. For the experienced scientist it offers a sin- gle-source reference to current developments and literature. Editoriai The ICP INFORMATION NEWSLETTER is edited by Dr. Ramon M. Barnes Professor of Chemistry University of Mas- sachusetts at Amherst with the assistance of a 20-member Board of National Correspondents composed of leading plasma spectroscopists. The Board members from around the world report news viewpoints and developments. Dr.Barnes has been conducting plasma research on ICP and other dis- charges since 1968. He also serves as chairman of the Winter Conference on Plasma Spectrochemistry sponsored by the ICP INFORMATION NEWSLETTER. Regular Features Original submitted and invited research articles by ICP Complete bibliography of all major ICP publications. Abstracts of all ICP papers presented at major US and inter- First-hand accounts of world-wide ICP developments. Special reports on dcp microwave glow discharge and other Calendar and advanced programs of plasma meetings. Technical translations and reprints of critical foreign-lan- Critical reviews of plasma-related books and software.and plasma experts. national meetings. plasma progress. guage ICP papers. Conference Activities The ICP INFORMATION NEWSLETTER has sponsored six international meetings on developments in atomic plasma spectrochemical analysis since 1 980 in San Juan Orlando San Diego St. Petersburg and Kailua-Kona. Meeting pro- ceedings have appeared as Developments in Atomic Plasma Spectrochemical Analysis (Wiley) Plasma Spectrochemistry and Plasma Spectrochemistry I/-lV (Pergamon Press) as well as in special issues of Spectrochimica Acta Part B and Journal of Analytical Atomic Spectrometry. The 1992 Winter Confer- ence on Plasma Spectrochemistry will be held in San Diego California January 6 - 11 1992; its proceedings will be published by Fall 1992. Subscription Information Subscriptions are available for 12 issues on either an annual or volume basis.The first issue of each volume begins in June and the last issue is published in May. For example Volume 17 runsfrom June 1991 through May 1992. Backissues beginning with Volume 1 May 1975 also are available. To begin a subscription complete the form below and submit it with prepayment or purchase information. For additional informa- tion please call (41 3) 545-2294 fax (41 3) 545-4490 or contact the Editor. Credit cards accepted. To order complete this section and send it to ICP Information Newsletter %Dr. Ramon M. Barnes Depart- ment of Chemistry Lederle GRC Towers University of Massachusetts Amherst MA 01 003-0035 USA. Start a subscription for the following issue IJ Volume(s)- (June 19- - May 19- ) or c7 19 (January - December). Enclosed 0 Prepayment 0 Check or money order ClVlSA 0 Mastercard Account No. (All 13 or 16 digits) D Purchase order NO.^ or 13 Send invoice. Date Cardholder Name Expiration date Cardholder Signature .Amount Due $ Mail to Name Organization Address City State/Countty ZI P/Postalcode Telephone Teledf ax Note For each credit-card transaction a 3% service charge will be added reflecting our bank charges. 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ISSN:0267-9477    

DOI:10.1039/JA99106000ia

出版商:RSC    

年代:1991

数据来源: RSC