摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 I VOL. 6 323 Analytical Evaluation of a Water-cooled Low Gas Flow Torch for Inductively Coupled Plasma Atomic Emission Spectrometry* Margaretha T. C. de Loos-Vollebregt C. N. Vanhoutte and Johan J. Tiggelman Laboratory of Analytical Chemistry Delft University of Technology De Vries van Heystplantsoen 2 2628 RZ Delft The Netherlands A water-cooled torch was installed in a Perkin-Elmer Plasma II inductively coupled plasma atomic emission spec- trometer for the operation of a low gas flow plasma with total argon consumption of 1.5 I min-'. Adjustments were required with respect to the coil and the nebulizer. The detection limits are about a factor of three higher than those obtained with the conventional torch in the same instrument.The stability of the system during a 2.5 h period of operation was equal to the conventional plasma. The linearity and linear range of the calibration graphs are also the same for both plasmas. No enhancement of interferences was observed in the low gas flow plasma. A labora- tory-built low gas flow plasma instrument was operated at generator frequencies of 27 40 and 54 MHz. At the higher generator frequencies the detection limits of the low gas flow plasma are improved by a factor of 2 in the wavelength range from 200 to 250 nm and up to a factor of 4 at higher wavelengths so that they become equal to the detection limits measured in the conventional plasma. Keywords Low gas flow plasma; water-cooled torch; inductively coupled plasma atomic emission spectrometry; interferences; generator frequency A drawback of conventional inductively coupled plasma atomic emission spectrometry (ICP-AES) is the high argon consumption of about 15 1 min-I.In order to reduce the argon gas flow several investigators have made successful attempts at reducing and optimizing the torch dimensions which has re- sulted in torches that can operate satisfactorily with an argon flow-rate of 7-8 1 min-'.'.' Reduction of the argon flow can also be achieved by cooling the torch externally with water or A water-cooled low gas flow torch has been used suc- cessfully in our laboratory with a laboratory-built ICP-AES in- strument for several years.x,9 A specific problem with the use of a low gas flow torch is the typical shape of the plasma which at an argon flow-rate of 12 1 min-I has a very long tail.Decreasing the argon flow to 4 1 min-I results in a stable smaller plasma. Between 2 and 4 1 min-' the plasma is unstable and below 2 1 min-' the plasma becomes stable again having a spherical shape with a hole in the centre. The low gas flow plasma is somewhat smaller than the con- ventional plasma. In the vertical position with side-on observa- tion radiation can be observed just above the coil through the outer tube but owing to ageing and formation of carbon de- posits on the outer tube the radiation transmitted through the quartz decreases. van der Plas et reported the use of a side tube installed on the outer tube of the torch observation through which eliminates loss of intensity. Alternatively good analytical results can be obtained with end-on observation of a low gas flow plasma in a horizontal water-cooled However most of the commercially available ICP-AES instru- ments are built to hold the torch vertically with side-on obser- vation of the plasma.Experimental A Perkin-Elmer Plasma I1 ICP spectrometer was used for part of the experiments. The instrument was equipped with two I m Ebert-type monochromators with gratings having 3600 and 1800 lines mm-' and a 27.12 MHz crystal-controlled gen- erator. The integration time was 100 ms. The instrument was operated with conventional and water-cooled low gas flow torches. * Presented at the Fifth Biennial National Atomic Spectroscopy Sympo- sium (BNASS). Loughborough UK 18th-20th July 1990. The influence of the frequency of the r.f. generator on the low gas flow plasma was studied using a laboratory-built ICP instrument with a horizontal water-cooled low gas flow torch.x A V-groove nebulizer with a gas orifice of 0.1 mm5J0 was used for the low gas flow plasma whereas sample introduction in the conventional plasma was performed using a V-groove nebulizer with a gas orifice of 0.2 mm All standard solutions were prepared from Merck standard solutions.Detection limits were measured using a Merck multi-element ICP standard solution. Construction and Optimization of the Water-cooled Torch The experiments were performed using two- and three-tube torch designs. The two-tube design [Fig. l(a)] was described in detail by de Galan and co-w~rkers.~.~ A 17 mm two-tube water-cooled torch was previously used in experiments with the laboratory-built instrument.8 The restrictors for the water cooling in Fig.l(a) were replaced by a third tube concentrical- ly placed between the outer and the inner tubes [see Fig. I@)]. The length of the water-cooled torches was 139 mm and the i.d. was 13 or 17 mm. The injector tube (0.5 mm id.) was made of a ceramic material (A1203). Both torches [Fig. l(a) and (h)] were operated at a total argon flow-rate of 1.5 1 min-' and a cooling tap water (12-14 "C) flow-rate of 2 1 m i d . For operation in the vertical position a quartz extension was placed on top of the torch with a viewing slot in front of the entrance slit of the monochromator [Fig. l(a) and ( h ) ] . Owing to the extension a somewhat longer tailed plasma was ob- tained which is required to observe the radiation.The water-cooled torch was mounted on a Perkin-Elmer 100 ml Scott-type spray chamber" with a low gas flow V- groove The gas orifice of this nebulizer was 0.1 mm and the hole for the sample supply was 1 mm. A stan- dard coil (i.d. 25 mm) and a larger 3-turn coil (i.d. 30 mm) were used. The intermediate argon flow-rate of the convention- al plasma ( 1 1 min-') was the same as the outer argon flow-rate for the low gas flow plasma whereas the outer argon flow was disconnected for operation of the water-cooled torch. The plasma was ignited with the usual start up sequence and the running conditions were intermediate argon flow-rate 1 1 min-I carrier argon flow-rate 0.4 1 min-I; power 1 kW; and observa- tion height above the load coil 15 mm.Under these conditions the water-cooled torch was run without structural damage. For324 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 1 VOL. 6 (a) ,- l - 1 r ’ ; Extension I I 1 I :tors ( b ) ,y-\ /\ r’( Extension \ Restrictor Water Argon tube I)--Injector U-Injector Fig. 1 Water-cooled low gas flow torch design with (a) two partial re- strictors attached to the inner wall and ( h ) with a third tube placed concen- trically between the outer and inner tubes analytical measurements optimization of the plasma condi- tions was required. A two-tube water-cooled torch (17 mm i.d.) gave a stable plasma with good analytical performance8.9 and had a lifetime similar to conventional torches (more than 1 year). For opera- tion of a water-cooled torch in the Plasma I1 instrument the maximum 0.d.of the torch is limited to 20 mm in order to fit the torch into the standard 3-turn coil. With a water-cooling jacket of 1 mm and for 1 mm wall thickness the i.d. of the torch is thus limited to 13 mm. Ignition and maintenance of the plasma in a 13 mm torch was easy and the analytical results in the early hours of opera- tion were very promising. Unfortunately after 25 h the water- cooling jacket cracked and broke. Several attempts were made to improve the lifetime by changing the cooling design but a longer lifetime was not obtained. A series of 17 mm torches with an 0.d. of 26 mm was tested. The standard coil was re- placed by a somewhat wider coil (30 mm) with the same number of turns.The matching network of the r.f. generator of the PI1 instrument was automatically retuned without significant increase of the reflected power. The torches were constructed according to the designs shown of Fig. l(a) and (h). The lifetimes of the 17 mm two-tube and 17 mm three- tube torches were satisfactory and no cracks were observed. Optimization of the ICP-AES spectrometer was performed for both the conventional plasma and the water-cooled low gas flow plasma. The signal to background (S/B) ratio was opti- mized for Mn (1 mg I-’) at 257.610 nm. Three parameters were varied for the high gas flow plasma power (0.9-1.4 kW); carrier argon flow-rate (0.8-1.5 1 min-I); and observation height (10-30 mm). A V-groove nebulizer with a gas orifice of 0.2 mm and an injector tube of 1.5 mm i.d.was used for the conventional ICP. Four parameters were varied for the low gas flow plasma power (0.9-1.4 kW); carrier argon flow-rate (0.2-0.37 1 min-I); observation height (0-10 mm); and ‘inter- mediate’ argon flow-rate (0.8-1.2 1 min-’). The results of the optimization are shown in Table 1. Results and Discussion Detection Limits Detection limits were measured for 16 elements using the 3s criterion. The optimized conditions for manganese (Table 1 ) were used to measure the detection limits. The results for the vertical low gas flow plasma with side-on observation are pre- Table 1 conventional torches Optimized parameters for ICPs operated in the low gas flow and Low gas flow Low gas flow Conventional side-on end-on* side-on Parameter Generator power/kW 1.1 0.6 1.24 Outer argon flow-rate/ 1 min-‘ 0 0 15 lntermediate argon flow-rate/l min-l 1.2 1.6 1 [Carrier argon flow-rate/ 1 min-I 0.26 0.26 1.1 Sample uptake rate/ ml min-l 0.5 0.5 1 Observation height/mm 4 - 19 * Reference 8.sented in Table 2. For comparison the corresponding results measured with a horizontal low gas flow plasma with end-on observation,* and a conventional plasma as well as the detec- tion limits reported by Winge et al.‘* are presented. The spec- tral bandpass of the monochromator was about 17 pm for all detection limits reported in Table 2. From the results in Table 2 it can be concluded that the detection limits for the low gas flow system are on average a factor of 3 poorer compared with the conventional plasma. For manganese the detection limit is 5 times higher.Dynamic Range The linearity and the dynamic range for manganese and calcium were measured from calibration graphs for several ion and atom lines. The graphs obtained using the low gas flow plasma are linear for up to 4-6 orders of magnitude. Stability The stability of the low gas flow system was tested by moni- toring the net intensity of manganese (1 mg I-’) at 257.610 nm for 2.5 11. Fig. 2 shows results for measurement of relative in- tensity plotted versus time. For comparison the same test was performed for the conventional plasma and the stability was similar. During the first hour of instrumental operation a de- crease in intensity of 20% was observed and after this warm- up period a stable signal was obtained.The relative standard deviation (RSD) (n=5) was measured for all the elements listed in Table 2 at a concentration of about 100 times the detection limit. The integration time was 0.1 s. Fig. 3 shows that the RSD values varied between 0.5 and about 1.5% over the wavelength range of 200-450 nm. Influence of the Generator Frequency Several workers have reported on the influence of the frequen- cy of the r.f. generator on the analytical performance of a con- ventional plasma.’-”’ At an increased frequency Capelle et al.” observed a decrease in the analyte emission intensity as well as a lower background intensity. The signal to noise ratio was improved and better detection limits were obtained at 56 MHz compared with 27 MHz” and at 100 MHz compared with 27 MHz.lS Alternatively Webb and Dent~n’~.” reported significantly poorer detection limits at 148 MHz compared with 27 MHz.The influence of the frequency of the r.f. generator on a low gas flow plasma was studied using a horizontal water-cooled torch in the laboratory-built ICP spectrometer. This instrument was based on a Jobin-Yvon 1 m Czerny-Turner monochroma- tor with a 17 pm bandpasx A 40.68 MHz crystal controlledJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1991 VOL. 6 325 Table 2 end-on observation and the conventional plasma. The monochromator bandwidth was about 17 pm for all the measurements Detection limits (30) (pg I-') measured in the vertical low gaj flow pla$ma with side-on observation the horizontal low gas flow plasma with Conventional. Conventional.Element Wavelength/ Low gas flow. Low gas flow. and line nm side-on end-on* P-E PII" Winge? Cr I1 Zn I1 Cd I1 Pb I1 Ni I1 Bi I I n I1 Fe I1 c o I1 B I Mn I1 Ga I Be 11 Cu I Ag I Ba I1 * Reference 8 . t Reference 1 1 . 205.552 2 13.856 2 14.438 220.353 22 1.647 223.06 1 230.606 238.204 238.892 249.773 257.610 294.364 3 13.042 324.754 328.068 455.403 27 5.8 5.0 38 14 141 149 16 6.8 6.7 1 .5 0.3 83 12 22 1.3 12 6.4 4.8 77 18 2 10 1 00 12 1 1 56 5.7 1 .o 0.5 6.4 1 .0 12 10 I .8 4.1 63 12 52 96 5.8 9.4 4.4 0.3 0.4 5.7 6.5 0.9 46 6.1 2.4 2.5 42 10 34 63 4.6 6.0 4.8 I .4 0.3 5.4 7.0 I .3 46 lS2 1.1 I O.* t 0.7 ' 1 I 1 60 80 100 120 140 160 Time/m i n Fig. 2 Stability measurements showing the relative intensity up to 2.5 h after a I h warm-up time A conventional plasma; and B low gas flow plasma.Each point refers to the average of ten intensity measurements Plasma Them r.f. generator was modified by RF Applications to operate also at frequencies of 27.12 and 54.24 MHz. At each geperator frequency an optimization for Mn at 257.610 nm was carried out using a univariate as well as a multivariate simplex method.Ix The parameters involved were the power the intermediate argon flow-rate the carrier argon flow-rate and the sample uptake rate. The image of the plasma was centred on the entrance slit of the monochromator. The results of the optimization are presented in Table 3. The analyte intensity was measured for all the elements that are listed in Table 2. The results are shown in Fig. 4 with the corresponding background intensities in Fig.5 . The analyte in- tensity is about the same for all generator frequencies whereas the background is significantly lower at higher generator fre- quencies. A decrease in the background intensity was observed for all emission lines in the wavelength region studied. The ratios of detection limits ( 3 0 ) measured at 40.68 and 27.12 MHz and at 54.24 and 27.12 MHz are presented in Fig. 6 for all the elements that are listed in Table 2. The detection limits are improved by a factor of 2 on average for both the 40.68 and 54.24 MHz frequencies and at higher wavelengths by a factor of 4. No improvement of detection limits is ob- served in the low wavelength region close to 200 nm. 2.0 1.5 1 s a - g 1.0 0.5 450 0 200 250 300 350 400 Wavelengthlnm Fig. 3 meawred with an integration time of 0.1 \ RSD\ measured tor 19 element\.based on five replicate\ and Michaud-Poussel and Mermet" discussed the reduction of the carrier argon flow which is required at higher frequencies of the r.f. generator. Because of reduced skin depth at a higher frequency the temperature in the centre of the plasma is lower therefore either the residence time in the plasma must be increased or the diameters of the coil and torch must be ad- justed. With a 0.5 mm injector tube the carrier argon flow-rate should be reduced from 0.2 1 min-I at 27.12 MHz to 0.1 1 min-' at 54.24 MHz which is too low for optimum performance of the nebulizer. In contrast with a 0.75 mm injector tube a carrier argon flow-rate of 0.2 1 min-' can be used successfully. Excitation Temperature The excitation temperature was measured in the conventional plasma and in the vertical low gas flow plasma with side-on observation.From the emission intensities of the iron lines ( 1 g 1-') reported by Blades and Caughlin,IY the usual Boltzmann plot of ln(/h'&l) ~'ei-.sz~.s E was constructed where 1 is the line intensity. h is the wavelength of the transition g is the de- generacy of the upper 1evel.f'is the oscillator strength and E is the excitation energy. The temperature was derived from the slope of this curve. The results are presented in Fig. 7 for dif- ferent observation heights In the conventional plasma the tem- perature is almost constant at 6100 K for observation heights326 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 1 VOL.6 Table 3 Optimized parameters for the manganese 257.610 nm line at dif- ferent frequencies. Measurements were performed with the low gas flow plasma and end-on observation described in reference 8. Intermediate Carrier Sample argon flow- argon flow- uptake Injector Frequency/ Power/ rate/ rate/ rate/ i.d./ MHz k W 1 min-' 1 min-' ml min-' mm 27.12 0.75 1.6 0.2 1.2 0.5 40.68 0.65 1.4 0.2 1 .o 0.6 54.24 0.63 0.9 0.2 1 .o 0.75 2 50 7 200 m S Y 150 U m 2 % 4- 100 .- In C a Y 5 50 x r" 200 250 300 350 400 450 500 Wavelengthhm Fig. 4 Analyte intensity of 19 elements measured at r.f. generator fre- quencies of A 27.12; Bi40.68; and C 54.24 MHz 18 16 14 12 r Y C U *$ 10 -.. - > C 'z 8 I I I I 1 200 250 300 350 400 450 500 Wavelengthhm Fig. 5 frequencies of A 27.12; B 40.68; and C 54.24 MHz Background intensity of 19 elements measured at r.f.generator between 13 and 23 mm above the load coil. At the optimum observation height (4 mm) of the low gas flow plasma (Table 1 ) the temperature is 7800 K. The shape of the curve in Fig. 7 confirms that the useful observation height of the low gas flow plasma is in the range of 2-8 mm above the load coil i.e. relatively low compared with the conventional plasma. Fig. 8(a) is a photograph of the conventional plasma. The shape of the plasma shows that it is easy to measure the emitted radiation above the torch. The low gas flow plasma is spherical and intense in the region inside the coil [Fig. 8(h)]. In the verti- cal torch configuration the plasma emission is measured just above the coil through the slot in the extension.It is clear that end-on observation of the spherical plasma is more attractive. The typical shape of the low gas flow plasma in a horizontal torch provides the advantage of an optically thin plasma. Interferences In order to evaluate interferences in the vertical low gas flow plasma the relative intensities of zinc magnesium and copper 1.2 I.' t x +# 1.0 E = 0.9 .$ 0.8 0.7 0.6 0.5 0.4 0.3 0.2 .- C U .- c. K 200 240 280 320 360 400 440 Wavelengt h/n rn Fig. 6 Ratio of the detection limits of 19 elements measured at r.f. gener- ator frequencies of 27.12 40.68 and 54.24 MHz A 40:27; and B 54:27 8000 5 7000 2 3 4 d P 6000 +- C 0 .- 4- +- .- 5000 w Annn -"- 0 4 8 12 16 20 24 Observation height/mm Fig. 7 above the load coil A conventional plasma; and B low gas flow plasma.The bars indicate the observation heights used in each of the plasmas Excitation temperature measured at different observation heights in the presence of increasing concentrations of potassium were measured. Fig. 9(a) shows that in the conventional plasma the emission intensities remain constant up to a potassium con- centration of 1 g I-' and decrease at higher concentrations. In the low gas flow plasma [Fig. 9(b)] all intensities remain con- stant up to 10 g 1-' of potassium. Conclusion From this study it was concluded that the use of a water-cooled low gas flow plasma with a total argon consumption of 1.5 1 min-' in a commercially available ICP spectrometer is feasible. The only adaptations were the changes of the torch the coil and the nebulizer.The two-tube and three-tube torches had the same lifetimes and showed similar analytical performance. The detection limits are about a factor of three poorer in the low gas flow plasma. The linearity of the analytical graphs and the stability of the signals are similar for the conventional plasma and the low gas flow plasma. Enhancement of interfer- ences was not observed. The detection limits using the low gas flow plasma can be improved by a factor of 2 at lower wavelengths and a factor of 4 at higher wavelengths by increasing the frequency of the r.f. generator from 27 to 54 MHz. Because the shape of the low gas flow plasma is smaller and spherical it is not easy to observe the emission above the torchJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1991 VOL.6 (a) ( 6) Fig. 8 Photographs of (a) the conventional plasma and ( h ) the low gas flow plasma *$ 0.8 w .- I $ 0.7 I 1 I 1 .- w I 1.1 - 1 .o; I C' I 0.9 0.8 V. I 0 0.01 0.10 1 .oo 10.00 Concentration of potassium/g I-' Fig. 9 Relative intensity measured in the presence of an increasing con- centration of potassium A. Cu B. Zn; and C. Mg. ( a ) Conventional plasma and (h) low gas flow plasma with side-on observation wall when the torch is in the vertical position. The measure- ment of the radiation required careful adjustment of the torch and the argon flows. End-on observation of a horizontal low gas flow plasma is easier to achieve and provides the same an- alytical performance. 327 The authors thank Perkin-Elmer Norwalk CT USA for financial support and A1 Angel and John Vollmer also of Perkin-Elmer for making the water-cooled torches.1 2 References Boumans P. W. J . M. and Hieftje G. M. in Induc,firely Coupled Plasma Emission S p e t m x o p j ed. Boumans P. W. J. M. Wiley New York 1987 pt. I ch. 5 p. 258. de Galan L. and van der Plas P. S. C . in Inducti\,eIy Coupled Plasmas in Analytical Atomic Spectrometry eds. Montaser A. and Golightly D. W.. VCH New York 1987 ch. 14. Ripson. P. A. M. and de Galan L. Spec.troi.hirrr. Acta Part B 1983 38 707. van der Plas P. S. C. de Waaij A. C. and de Galan L. Spectrochim. Acta Part B 1985 40 1457. van der Plas P. S. C. and de Galan L.. Spe(,troc.him. Actu Part B 1984,39 1161. Kawaguchi H. Tanaka T. Miura S.. Xu J. and Mizuike A.. Spec- ti-ochim.Aim Part B 1983 38 13 19. Ripson P. A. M. Jansen L. B. M. and de Galan L. Anal. Chem. 1984,56,2329. de Loos-Vollebregt M. T. C.. Tiggelman. J. J . and de Galan. L. Spectimhim. Acta Part B 1988. 43 773. de Loos-Vollebregt M. T. C. Tiggelman J. J. Bank P. C. and De- graeuwe C.. J . Anal. At. Spectrom.. 1989,4 2 13. Ripson P. A. M. and de Galan L. Spet.trot.him. Ai,ru Part B 198 I 36 71. Scott R. H. Fassel V. A. Kniseley R. N. and Nixon. D. E.. Anal. Chem. 1974 46. 75. Winge R. K. Fassel V. A. Peterson V. J. and Floyd M. A Indirc- tiid?. Co~pled Plasma Atomic Emission Spetwisiwpy. An Atlus of Sper.tra1 Irlformafion Elsevier Amsterdam 1985. Capelle B.. Mermet J . M. and Robin. J.. AppI. Spe(wo.w.. 1982 36 102. Michaud-Poussel E. and Mermet J. M.. Spectroc.him. Acta. Purr B 198641 125. Michaud-Poussel E. and Mermet J . M.. Specwochim. Acta Part B 1987,42 I 163. Webb B. D. and Denton M. B . Spec.ti.ochirn. Acta Part B. 1986 41 361.328 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 1 VOL. 6 17 Webb B. D. and Denton M. B. J . Anal. At. Spectrom. 1987,2 21. 18 van der Wiel P. F. A. Kateman G. and Vandeginste B. G. M. Chemnmetr-id Optimization by Simplex Elsevier Scientific Soft- ware Amsterdam 1985. 19 Blades M. W. and Caughlin B. L. Spec.rr.nc.him. Actu Part B 1985 40. 579. Paper 0105423B Received December 3rd 1990 Accepted February 4th I991

ISSN:0267-9477    

DOI:10.1039/JA9910600323

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

329 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1991 VOL. 6 Rotating Disc Nebulizer for Inductively Coupled Plasma Optical Emission Spectrometry Cor J. Rademeyer C. S. Collins and L. R. P. Butler Department of Chemistry University of Pretoria Pretoria 0002 South Africa A rotating disc nebulizer of apparently unique design has been developed for use in inductively coupled plasma optical emission spectrometry. The fundamental component is a rotating disc onto which the liquid or slurry sample is introduced. It is easy to construct requires no additional spray chamber is easy to operate effectively and is blockage free. Aerosols with mean droplet diameters of approximately 0.50 pm are produced. Furthermore the aerosols are homogeneous with up to 80% of the droplets having diameters no larger than 0.6 pm.Unfortu- nately the aerosol transport efficiency is poor this has a detrimental effect on the detection limits sensitivity and stability. Principles of operation are described aerosol production and analytical performance are evaluated. Keywords Rotating disc nebulizer; inductively coupled plasma optical emission spectrometry; nebulization; aerosol production Inductively coupled plasma optical emission spectrometry (ICP-OES) is one of the most popular techniques in modem analytical chemistry. Favourable analytical aspects of the plasma are well documented. However a major limiting factor is the sample introduction. The process of the plasma in atomizing and exciting an analyte is worthless if the analyte cannot be introduced in an appropriate form into the plasma.The complexity of the problem is aggravated by the many different forms that samples can assume e.g. solids powders slurries or solutions. As most samples can be converted into solutions nebulizers which allow injection of the solution into the plasma as an aerosol emerged as the chief sample introduc- tion device. Conventional pneumatic nebulizers alleviated the problem but did not eliminate it. Samples come in different forms and it is not unusual to have a sample solution with par- ticulates or a high salt content. Both these conditions tend to cause blockages of the injector nozzle. A host of other draw- backs have been found ti=. memory effects large sample volume requirements instability and poor efficiency and nebu- 1 izat ion.34 Despite these limitations pneumatic nebulizers remain the most popular means of sample introduction in ICP-OES. At- tempts to improve performance have resulted in a range of nebulizers. Most are based on the use of a pressurized gas flow that is either concentric with or perpendicular to the sample flow in order to shatter the sample solution into droplets. These pneumatic nebulizers are particularly prone to blockag- es as the sample must pass through small orifices and nozzles. Modifications in order to try to eliminate the problem with varying measures of success have produced the Babington and V-groove nebulizers. 12.4.6 Nebulizers based on other princi- ples have also been studied e.g. ultrasonic jet impact and glass-frit nebulizers. All have their merits and all have their drawbacks .3,4.h-R A nebulizer for use in ICP-AES has recently been developed in this laboratory.Unlike commercially available systems the nebulizer is not based on pneumatic or ultrasonic principles. The fundamental component producing the aerosol is a rotat- ing disc. Aerosol production by means of planar spinning discs for purposes other than ICP-OES has previously been report- ed.9.10 Whitby et al.9 experimented with the use of spinning disc aerosol generators as early as 1965. Homogeneous aero- sols of droplets with diameters in the range from 0.5 to 30 pm were generated. Despite achieving aerosol production in this manner various drawbacks were evident. Furthermore the general design differed somewhat from the model proposed here being much larger and more complicated.The applica- tion of these earlier models was far removed from spectrosco- py being the generation of aerosols used for testing gas cleaning filters. More recently Mehrhardt and Brauer’O investi- gated nebulization with the use of discs as part of an engineer- ing study of heat and material exchange processes. They de- scribed a comprehensive mechanical study. A rotating disc as discussed above would appear to be ade- quately suited to the production of aerosols. Greenfield et al.” mentioned that they found no particular advantages in the use of a spinning disc nebulizer during their experiments. However they did not elaborate and no details concerning either design or analytical results were given. An ICP-OES nebulizer unit based on the rotating disc principle has now been designed in this laboratory.The unit features the genera- tion of aerosols of suitable dimensions within a framework of operating parameters compatible with those of an ICP. Theory of the Rotating Disc Nebulizer A drop of fluid placed on the centre of the rotating disc surface will be subject to the forces of circular motion as experienced by the point of the disc surface on which it is positioned pro- vided it adheres to the disc. The drop will also experience mass air resistance and contact forces. However radial accel- eration is largely dependent on the frictional force opposite to the direction of motion. As the drop is momentarily at rest with respect to the point of the disc surface the maximum fric- tional force attainable is determined by the product of the coefficient of static friction mass and gravitational accelera- tion.Hence a certain maximum velocity due to centripetal ac- celeration can be attained. This in turn defines a certain critical angular velocity. If this critical angular velocity is exceeded the drop will slide across the disc surface following a curved path. The maximum frictional force will then be determined by the coefficient of kinetic friction with a magnitude of less than that of the static coefficient. This reduction of frictional force prevents the drop from slowing down again. Should the disc be surrounded by a wall the drop will collide with this wall shattering into finer droplets. It can be deduced that the droplets should preferably leave the surface of the disc at the edge in order to experience the greatest tan- gential acceleration thereby colliding with the walls with greater impact.Another process that can lead to the formation of an aerosol concerns shock waves. Should the frequency of the disc be such that the outer edge attains the speed of sound ultrasonic shock waves will be induced in the fluid reaching that point. Consequently spontaneous shattering of the drops into a fine aerosol will occur. However in order for this supersonic shat- tering to occur the edge of a disc with a diameter of 60 mm must rotate at a minimum frequency of 101 859 rev min I placing a heavy mechanical load on the system.330 A t c ’ > tc- -_ JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 I VOL.6 t gas flow t = - J B B L f A- 3 1 Fig. 1 and B disc Schematic representation of gas flow in cross-section. A motor; Rotating disc Nebulizer housing - . . . . . . . . . . . . . . . . . . ’ . . . . A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig 2 Schematic representation of the rotating disc nebulizer A motor; B disc; C sample introduction D argon inlet; E aerosol outlet; and F drain Laws of aerodynamics predict that particles in the region above a disc rotating at high frequency will be swept out- wards creating a region of reduced pressure above the surface of the disc. A gas flow introduced centrally above the disc will counteract this. It can be expected that a gas flow introduced into this region will spiral outwards and upwards to exit through the upper outlet as shown in the cross-sectional view of Fig.1. Droplets formed at the perimeter of the disc are swept upwards away from the disc by the gas flow and inevi- tably turbulence will occur. The nature of this turbulence would seem to affect the quality of the aerosol. This factor will be discussed in the light of the experimental evidence given below. Commercially available nebulizer systems combine a device for producing an aerosol e.g. a cross-flow nebulizer with a spray chamber to refine the aerosol. Unlike these systems the rotating disc nebulizer incorporates the nebulizing mechanism within the spray chamber forming a compact self-contained unit. The proposed nebulizer has been optimized for physical performance and related parameters.These factors are dis- cussed in this paper. The analytical performance of the nebu- lizer has also been investigated and the evaluation is reported. A schematic diagram of the proposed rotating disc nebulizer is shown in Fig. 2. The motor A is used to drive the 60 mm diameter disc B at frequencies of up to 55 000 rev min-’. A ta- chometer is incorporated in the design in order to measure the speed of the disc. Sample is fed onto the centre of the disc through the needle C situated above the disc. A peristaltic pump is used to maintain a continuous controlled sample flow-rate. As mentioned before the nebulizer and spray chamber form a single unit the Perspex housing of specific geometry includes the spray chamber. Gas is conducted into the chamber through the fixed tube D centrally situated above the disc and exits through the concentric outlet E at the upper edge.Excess of sample drains away through the outlet at the lower edge F. Results and Discussion Evaluation of Physical Aerosol Production As was expected various parameters were critical to the aerosol production performance of the nebulizer. The effects of the following parameters were studied gas flow-rate; sample solution flow-rate; disc rotation frequency; spray chamber geometry; disc surface character; and the configuration of gas flow introduction and aerosol outlet points. Each parameter was investigated for tendencies and optima. The ICP emission signal is directly proportional to the number of atoms excited in the plasma. For atoms to be avail- able for excitation then complete desolvation vaporization and atomization must first occur.Theoretically presenting smaller droplets to the plasma should allow these processes to proceed more efficiently than for larger drops. Consequently design parameters were evaluated in terms of the droplet diameters produced and the droplet size distributions. Droplets were measured with the aid of a Micro Laser Particle Spectrometer (p-LPS) Particle Measuring Systems Boulder CO USA. The instrument provided droplet diameter data based on the scatter- ing of aerosol particles intercepting a laser beam. The aerosols were measured as they left the outlet of the nebulizer assembly (Fig. 2 E). Although specific liquid properties such as viscosi- ty will influence disintegration processes the studies described were conducted using water as this is the most common solvent it was assumed to be a good indicator of general ten- dencies.Aerosol droplet diameter distributions were used as profiles as the main objective of this part of the study was to provide insight into the aerosol producing tendencies and the dependencies thereof. As aerosol formation occurred within the spray chamber the geometry of the chamber was expected to be of major im- portance. It was found to be the most important physical para- meter apart from the disc. After leaving the disc edge droplets travel a certain distance then collide with the spray chamber walls. They are then swept upwards through the chamber ultimately exiting through the aerosol outlet. If at any stage they become too heavy to be carried by the gas flow they fall back to exit via the drain. It follows that there are several geometric considerations (i) the distance between the disc edge and the spray chamber wall to be traversed; (ii) the angle of the spray chamber wall forming the collision surface; (iii) the distance to the aerosol outlet; (iv) the geo- metry of the area through which the drops must pass in order to reach the aerosol outlet; and (v) the geometry of the aerosol outlet.The basic shape of the spray chamber can be seen from the schematic diagram of the nebulizer given in Fig. 2. An investi- gation of spray chamber geometry was conducted by using ex- perimental Perspex spray chamber fittings which could slide into the basic square-shaped cavity.The results of this series of aerosol measurements were graphically displayed in order to obtain profiles which illustrated the various geometric aspects. The repetition of the measurements at alternative disc frequencies and liquid delivery rates further clarified the rela- tion between the influence of these parameters on aerosol pro- duction and geometric configuration. As the data so obtained were fairly extensive only the most relevant results are given and illustrated in Figs. 3-7. The optimum geometry for aerosol production emerged as that allowing a distance of 2.5 mm from the disc edge to the spray chamber and providing a perpendicular spray chamber wall as the collision surface. It was evident that the geometryJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 1 VOL. 6 33 1 Distance m 0.5 mm 1.5 mm 2.5 mm 3.5 mm 4.5 mm 70 60 - 50 $ 40 0 30 C r-" 20 10 0 Droplet diameter/pm Fig.3 flow-rate of 1 1 min-' and disc frequency of 24000 rev min-' Effect of the distance between the spray chamber wall and the disc edge on droplet distributions for water at an uptake rate of 2.5 ml min-' gas 25 / I I Angle 31" =goo 110" " I 0.30 0.35 0.40 0.45 0.50 1.00 1.20 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 Droplet diameter/pm Fig. 4 1 1 min-' and disc frequency of 24000 rev min-' Aerosol droplet distributions obtained with spray chamber walls of various angles with water at an uptake rate of 2.5 ml min-I gas flow-rate of of the spray chamber was a decisive factor and to a large extent determined the effects of the other operational parame- ters.The following explanations are suggested. With respect to Fig. 3 providing a greater distance for droplets to cross between the disc edge and the spray chamber wall allowed droplets to lose momentum impact with the spray chamber wall was thus less forceful. However a distance of less than 2.5 mm increased the aerosol density encouraging collisions and recombination of the droplets to form larger drops which were more likely to fall back and drain away. Bearing in mind that the angle of the spray chamber wall influenced the manner of collision the superiority of a perpen- dicular surface can be readily understood (Fig. 4). Both the acute angle and the obtuse angle surfaces would have allowed droplets to glide away more easily on impact than the perpen- dicular surface.The apparent superiority of the acute angled wall to the obtuse angled wall was probably attributable to the greater ease with which droplets could run off to drain rather than continue upwards against the wall to the aerosol outlet. Consequently fewer droplets reached the outlet than with the obtuse angled wall. A gas flow was necessary for aerosol transport. The gas flow could be introduced from either above or below the disc at dif- ferent positions. It was determined that an introduction point located centrally above the disc surface afforded the best com- promise in terms of the amount and quality of the aerosol. This is in accordance with the discussion above which indicates that the introduction of the gas in this way counteracts the region of reduced pressure formed encouraging an outwards and upwards spiralling of the aerosol in the chamber without interfering with the aerosol outlet or the drainage of any excess of sample. It was also evident that although the gas flow was not re- quired to generate aerosols as for pneumatic nebulizers it influenced the quality of the aerosol. Besides the position of the point of introduction the flow-rate was significant. Flow- rates of from 1 to 3 1 min-' were advantageous while higher flow-rates were detrimental as can be seen from Fig.5. It is probable that low flow-rates allowed the smooth semi-circular aerosol movement described above (Fig. l) whereas high flow-rates induced excessive turbulence above the disc surface. Radial aerosol movement would have encouraged collision of the droplets with the spray chamber wall the drops would then332 L 3 2 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE I99 1 VOL.6 1 I 1 T I .- 2 l o t \y Fig. 5 Effect of gas flow-rate on the percentage of drops with diameters not exceeding 0.3 pm produced with water at an uptake rate of 2 ml min-I and a disc frequency of 24000 rev min-’ -0 2 50 a v) Q g 40 L .I- m m 30 5. 20 1 1.5 2 2.5 3 3.5 4 Sample flow-rate/ml min ’ 2 Fig. 6 Effect of sample flow-rate on the percentage of drops with diame- ters not exceeding 0.3 ym. produced with water at a gas flow-rate of 1 1 min-’ and a d i x frequency of24 0o0 rev min-’ continue upwards to the exit. Further turbulence would not only have disturbed the aerosol flow but would also have swept away any droplets of fluid which had lost contact with the disc surface either to exit before further shattering or to re- combine into larger drops.The effects of gas flow-rates were found to be highly dependent on the geometric configuration of the spray chamber. Therefore it is likely that the phenomenon observed at a flow-rate of 2 1 min-’ in Fig. 5 is indicative of an interaction with a particular geometric configuration. Sample flow-rate was found not to be as significant a factor as geometry or gas flow-rate as illustrated in Fig. 6. The flow- rate had to be sufficient for aerosol formation; flow-rates of less than 2 ml min-’ were not acceptable. Higher sample Aow- rates appeared to produce ‘overloading’ of the disc surface in other words there was a limit to the amount of fluid that could make contact with the disc surface.Excess of fluid would have run off either to drain or as large drops. Interesting observations were made concerning disc fre- quency. In general performance was improved at the lower frequencies as can be seen from Fig. 7. Apparently fluid re- mained in contact with the disc surface for longer at low fre- quencies than at high frequencies as was expected from the discussion concerning the forces acting on the fluid. Droplets that lost contact with the surface closer to the centre of the disc were less likely to collide with the wall. Furthermore these larger drops formed at higher frequencies were caught above the disc and left the chamber as part of the aerosol instead of draining away.As discussed above acceleration from stand-still would lead to a proportional increase in the acceleration of fluid as it neared the edge of the disc proving beneficial to aerosol pro- duction until a certain critical angular velocity was reached. \ 0 10 20 30 40 Disc frequency1 x lo3 rev min-’ Fig. 7 Effect of disc frequency on the percentage of droplets with diame- ters not exceeding 0.3 pm produced with water at an uptake rate of 2.5 ml min-I and a gas flow-rate of 1 1 min-I Acceleration beyond this velocity caused fluid to glide over the surface detrimentally affecting aerosol production. High- speed photography actually showed this occurring. It appeared that the critical angular velocity was reached between 15000 and 35 000 rev min-I depending on the interaction between the fluid and the disc surface.Several adaptations of the disc were investigated. In an attempt to increase adhesion between the disc surface and the fluid discs with roughened surfaces and some made of differ- ent materials were studied. Discs with perforations and curved engravings approximating the path that the liquid would follow on the surface were also investigated. Although slight differences were observed no real improvements were found. However many other possibilities are still open to investiga- tion e.g. a toothed wheel (as employed in agricultural spray- ers). Some discs were coated with polytetrafluoroethylene in order to protect them from attack by acid solutions. The smoother the texture of the surface of a disc however the more drastically reduced was the beneficial physical contact between the sample and the disc surface.Although number density distributions were used during the investigation of physical parameters droplet diameter distribu- tions obtained under favourable operating conditions were translated into mass distributions. These mass distributions in- dicated that the majority of the sample was contained in very small droplets; up to 80% of the aerosol sample mass was composed of droplets with diameters of 0.6 pm or less mean droplet diameters being no greater than 0.5 pm. Under optimum operating conditions the droplet distributions were also narrow with cut-off diameters of less than 4 pm. Compar- ison with the other available nebulizers was not possible as their aerosol densities exceeded the measuring capacity of the p-LPS.Evaluation of Analytical Performance Obviously it is desirable that as much analyte as possible reaches the plasma. Consequently the aerosol transport efficiency of the nebulizer was quantified. As the rotating disc nebulizer is a single unit the aerosol leaving the aerosol outlet is that which proceeds to the plasma without further refinement aerosols were directly measured. A collection tube filled with silica gel was attached to the aerosol outlet pipe. A container was also placed at the drain outlet. A flask containing the liquid to be sampled the drain collection con- tainer and the silica gel collection tube were weighed. The sample liquid was aspirated for a certain timed period. All three containers were then re-weighed. The nebulizer trans- port efficiency was calculated from the ratio of the mass dif- ferences of the aspiration liquid container and the silica gel collection tube.Initially efficiency varied by up to approxi-333 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1991 VOL. 6 Table 1 determination of analytical performance Inductively coupled plasma operating conditions used for the Parameter Power 1 W Coolant gas flow / 1 min-l Auxiliary gas flow 1 1 min-l Nebulizer gas flow / 1 min-I Nebulizer pressure I Pa Number of measurements Integration time 1 s Me i nh ard nebulizer I300 12-14 0.5-1 0.8 2.2x105 20 10 Cross-flow nebulizer 1300 12-14 0.5-1 0.8 2.2x 105 20 10 Rotating disc nebulizer 1300 12-14 0.5-1 1 20 10 - Table 2 in ppb Detection limit$ at the 95% confidence level.Values given are Element Wavelengthhm Ca cu Cr A1 Fe Si Pb Se P 370.603 324.754 267.7 16 308.2 15 259.940 25 1.6 1 1 220.353 196.090 178.270 Mei n hard nebulizer 7.0 5.6 3.4 4.5 27 35 44 122 33 Cross-flow nebulizer 5.3 4.6 4.5 6.0 31 28 60 120 26 Rotating disc nebulizer I l l 118 43 516 20 73 187 337 I69 Table 3 rotating disc nebulizers Relative standard deviation values for Meinhard cross-flow and Element Wavelengthlnm Meinhard Cross-flow Rotating disc nebulizer nebulizer nebulizer Ca cu Cr Al Fe Si Pb Se P 370.603 325.754 267.7 16 308.2 15 259.940 251.61 1 220.353 196.090 178.270 0.9 1 1.2 1 .o 0.87 1.2 1.8 1 .5 1.1 1.4 1.1 0.7 I 1.2 1 .o 1.1 1 .5 1.4 1 .5 13 4.3 6.1 3.6 6.2 3.7 5.2 3.2 5.6 15 mately 2%. Unfortunately once a final design in respect of aerosol production had been completed reproducible efficiency measurements were approximately only 0.5%.This was not surprising as it could be seen that a large amount of the aerosol produced within the chamber was not drawn off. Indeed the greatest single problem associated with the design is the successful removal of the aerosol from within the unit. In order to evaluate the analytical merit of the rotating disc nebulizer ICP emission signals obtained when using it were compared with those obtained when using two other commer- cially available nebulizers a cross-flow and a Meinhard. The latter two nebulizers were both used in conjunction with a con- ventional Scott spray chamber. A Spectro Analytical Instru- ments ICP-OES instrument was used throughout for ICP determinations. Operating conditions are listed in Table I for each nebulizer.A selection was made from the emission lines available on the polychromator. These wavelengths are specified in Table 2. Multi-element standards of Ca Cu Al Cr Fe Si Pb Se As and P were used. All solutions contained 20 pg ml-' of Sc as an internal standard in a 5% HNO matrix. Four separate sets of data were obtained for each nebulizer. Emission data were corrected by using the internal standard ratio and blank subtractions made. Sensitivity curves were produced from these the sensitivities were deduced and used in the calcula- tions of the detection limits. The actual experimental back- ground variations were always used no assumptions were made.The detection limits are summarized in Table 2. Deductions concerning stability were made from the accumulated data. Relevant indicators are given in Table 3. It is evident that the rotating disc nebulizer did not compare favourably with the other two nebulizers in terms of analytical performance. The high relative standard deviations of the rotating disc nebulizer compared with those of the other two nebulizers are consis- tent with the disappointing detection limits. However poor an- alytical results were to be expected in the light of the limited aerosol transport efficiency. It was evident that aerosols did not penetrate the plasma in the same manner as those from the other two nebulizers. Obviously this failure had a direct bearing on the analytical deficiencies.It is a tribute to the high quality of the aerosols that the analytical results are not even worse than those observed. A further drawback was the memory effect arising from the relatively large spray chamber volume. Although not quantified this effect was evident during experimental use a pre-flush period of 30 s being required before measuring new samples. Conclusions The rotating disc nebulizer produced in this laboratory presents a challenge. The basic nebulizer construction was op- timized in terms of physical parameters with regard to aerosol production. Fine homogeneous aerosols were produced. Un- fortunately the analytical performance proved disappointing. It was evident that the major limiting factor was the inefficiency in the aerosol transport to the plasma.There was no doubt that sufficient amounts of high-quality aerosol were being produced however the aerodynamic design in relation to the ICP system prevented the bulk of the aerosol from reaching the plasma obviously aerodynamic refinement is re- quired. This aspect is more complicated than at first suspected and will require a certain degree of relevant expertise. However it seems that if a solution can be devised it will be well worth it. In view of the deficiencies of the nebulizer the experimental slurry work was brief and served merely as an indicator of the potential of the nebulizer. The results using the rotating disc nebulizer without any special refinement were unexpectedly good. The nebulizer appears to hold great promise for this application particularly if the aerodynamic defects can be remedied. References I 2 3 4 5 6 7 8 9 LO 1 1 12 Sharp B. L. J . Anal. AT. Spectrom. 1988. 3. 613. Thelin B. Atiuljst. 1981. 106. 54. Cecconie T. Muralidharan. S. and Freiser I i . Appi. S p e ~ ~ r o s ~ ~ . 1988.42 177. Ebdon. L.. and Cave M. R.. Analyst 1982. 107 172. Nixon. D. E. and Smith G. A.. Anul. Chern.. 1986.58.2886. Layman L. R.. and Lichte F. E. Anul. Chem. 1982 54 638. Doherty. M. P. and Hieftje G. M. App/. Spec'trosc. 1984 38. 405. Fassel V. A,. and Bear B. R.. Spectroc.him. Actu Part B.. 1986. 41 1089. Whitby. K. T. Lundgren. D. A. and Petercon. C. M. Itit. ./. Air Wuter. Pollirt. 1965 9. 263. Mehrhardt. E. and Brauer H.. Forx3h. I~igeriieitrM.~.s. 1980 46. 26. Grccnfield. S. Jones. 1. L. McGeachin. H. M. C. D.. and Smith P. B.. Aiial. Chim. Acru. 1975 74 225. Willis. J. B.. A w l . Chem.. 1975. 47 1752. Pupei- 9104339J Rec-ei\'ed October- I I th I990 Accepted Januui-y 3 0 t h 1991

ISSN:0267-9477    

DOI:10.1039/JA9910600329

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 1 VOL. 6 335 Determination of Thorium and Uranium in Total Diet Samples by Inductively Coupled Plasma Mass Spectrometry Kunio Shiraishi," Yuichi Takaku,b Katsumi Yoshimizu," Yasuhito Igarashi," Kimihiko Masuda,b James F. Mclnroyd and Gi-ichiro Tanaka" a Division of Radioecoiogy National Institute of Radiological Sciences 3609 lsozaki Nakaminato lbaraki 3 I 1 - 72 Japan bMarubun Company 8- 1 Nihonbashi Odenma-cho Chuo-ku Tokyo 103 Japan cJapan Chemical Analysis Center 295-3 Sannou-cho Chiba-shi 28 7 Japan *Health and Environmental Chemistry Group Los Alamos National Laboratory Los Alamos NM 87545 USA The Th and U contents in total diet samples were determined by inductively coupled plasma mass spectrometry (ICP-MS). The internal standardization method was adopted to compensate for non-spectral interferences arising from matrix elements in the sample solutions.Concentration levels of the order of pg ml-' of Th and U in the total diet sample were determined easily and rapidly by using Bi as an internal standard. The mean concentrations and standard deviations of Th and U in the total diet samples were found to be 25 k 12 and 44 k 20 ng g-' of ash respectively (for n = 62). Keywords Thorium determination; uranium determination; dietary intake; inductively coupled plasma mass spectrometry; matrix effect Inductively coupled plasma mass spectrometry (ICP-MS) is be- coming a popular technique for determining trace and ultra-trace elements.'.' Although a disadvantage of ICP-MS is mass spectral interference (isobaric interference) it offers most of the versatil- ity required for elemental analyses today i.e.lower detection limits a wider choice of isotopes to be determined and also the capability of analysing isotopic ratios. In contrast to convention- al spectrometric techniques such as inductively coupled plasma atomic emission spectrometry (ICP-AES) and atomic absorp- tion spectrometry this technique does not suffer from spectral inteferences to the same extent. Radioactivity measurements in- cluding neutron activation analysis require special instrumenta- tion for the activation source and chemical separation. However chemical separation is rarely needed for ICP-MS measurements owing to the low detection limits possible. Inductively coupled plasma MS has been applied to both si- multaneous multi-element analyses and isotope ratio analyses of biological materials,3-s but seldom to analysis of diet samples.6 Studies have been carried out to establish the daily intake of elements from the point of view of radiological pro- t e ~ t i o n .~ . ~ In this paper the determination of 232Th and *W at pg ml-' levels in diet samples by ICP-MS are described. Experimental Instrumentation The ICP-MS instrument used was a VG Isotopes PlasmaQuad PQ2 Plus installed at Marubun Tokyo Japan. Some specifications of the instrument and the operating conditions employed are summarized in Table 1. An alpha-spectrometer Camberra Series 35 Plus 4096-channel analyser equipped with a 300 mm' silicon surface barrier detector was used only for the determination of U.Reagents Tamapure-AA grade acids (nitric hydrochloric perchloric and hydrofluoric) and hydrogen peroxide were obtained from Tama Chemicals (Kawasaki Japan). Standard solutions of Th U and Bi were prepared from Spex single-element standard plasma solutions 1000 pg ml-' (Spex Industries Edison NJ USA). Freshly purified water (resistivity 18 MQ cm) was pre- Table 1 Operating conditions for ICP-MS Instrument- VG Isotopes PlasmaQuad PQ2 Plus Mass analyser Number of channels 1024 Number of scan sweeps 1200 Dwell time Analysis time Approximately 3 min Mass regions skipped Scan mass range 207.98-240.60 u 320 ps per channel 210.0&230.00 and 233.00- 237.00 u Plasma torch- Frequency R.f. power Position for ion extraction Coolant gas flow Auxiliary gas flow Carrier gas flow Sample uptake rate Nebulizer 27.12 MHz 1.20 kW 7 mm from load coil 13.0 1 min-' 0.5 1 min-' I 1 1 min-' 0.5 ml min-' Concentric glass type pared from tap water using a Bamstead D-2794 four- module system (Boston MA USA). Sample Preparation Diet samples were collected twice from 31 prefectures in Japan in 1981-1982 by using a duplicate portion study. Each sample consisted of the total of the whole of the daily meals collected from five adult males in one sampling place. The whole diet samples were dry ashed in a muffle furnace at a final temperature of 450 "C. The ash was powdered and mixed using an agate mortar and pestle until homogeneous. Preparation of the sample solutions for ICP-MS was as follows. Working in a chemical hood (class loo) a portion of approximately 0.25 g ash was digested with a mixture of 2 ml of concentrated nitric acid and 0.5 ml of perchloric acid in 3 50ml borosilicate beaker on a ceramic hot-plate until only a white residue remained.The residue was dissolved in 7% nitric acid transferred into a 25 ml borosilicate calibrated flask and diluted to volume with freshly prepared de-mineralized water. The final nitric acid concentration was adjusted to 10%. National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 157 1 Orchard Leaves336 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 1 VOL. 6 5. \ 800 .- 4- 2 w C al 5 400 X .- I (10.28 g) was dry ashed in the muffle furnace at 450 "C. This ash was treated by almost the same procedures as described above except for an additional treatment with hydrofluoric acid in a Teflon beaker.After evaporating the solution to dryness the residue was dissolved in 100ml of 10% nitric acid and later diluted ten-fold for the measurements. - - ICP-MS Measurements Bismuth was chosen as an internal standard based on the results of previous studies.8 The diet sample solution was diluted ten-fold before the determination. Bismuth solution (10 pg ml-I) was also added to all solutions to give a concentration of 100 ng ml-I. A calibration graph was prepared using five concentration levels of the standard solutions 0 10 50 100 and lo00 pg rnl-l in addition to the internal standard. Isotopes of 2wBi 232Th and 238U were measured in the present study. Each sample was measured three times.U u I 1 1 I I I 1 I Recovery Tests Recovery tests for Th and U were carried out by using one of the diet samples in a similar manner to that described above. For each diet sample 2.5 ml of a 10 ng ml-I standard solution were added to a portion (0.25 g) of the diet ash before diges- tion. Both spiked and non-spiked samples were analysed in triplicate. Determination of *W by Alpha-Spectrometry For one diet sample the 238U concentration was determined by alpha-spectrometry. Ten grams of diet ash were dissolved in 9 mol dm-3 hydrochloric acid along with a tracer 232U (activity 0.01 counts s-I). The radionuclides were isolated by anion ex- change (using Bio-Rad anion-exchange resin AG 1-X4 Bio- Rad Laboratory Richmond VA USA) and electroplated onto a stainless-steel planchet and measured for 210000 s by alpha- spectrometry.The procedure has been described in detail else- where .9 Results and Discussion Accuracy and Precision The NIST SRM 1571 was analysed along with the diet samples. The results are shown in Table 2. Consensus mean and standard deviation (values reported by Gladney'O) are also included. The results 60.2 pg g-' for Th and 29.9 pg g-l for U were in good agreement with the certified and consensus values. The detection limits for Th and U in this study are defined as three times the square of the error counts obtained in the measurements of a blank solution and were 1.3 and 2.9 pg ml-l respectively. Recovery Tests For the recovery measurements added element concentrations were 100 ng ml-I based on initial solutions of 25 ml which Table 2 Results for NIST SRM 1571 Orchard Leaves Concentration* / pg g-' dry mass Element Present result Certified value Consensus valuest 232Th 60.2 kO.5 6 4 f 6 58 ( 3 ) 2 3 X U 29.9 f 0.5 29 k 5 28 + 3 (7) * Mean k standard deviation for three measurements.t From Gladney reference 10 numbers in parentheses are number of data used to obtain consensus values. were then diluted ten-fold. For Th spiked and non-spiked samples were found to be 115 f 15 and 17 f 0.8 pg ml-I re- spectively. For U spiked and non-spiked samples were 396 f 3 and 298 f 0.4 pg ml-I respectively n = 3. Good recovery (98%) was obtained for both elements. Effects of Matrix Concentration Although lower detection limits is one of the merits in ICP- MS non-spectral interferences (matrix effects) must be taken into consideration to obtain good analytical data.x The salt content of samples to be analysed should be diluted as much as possible to prevent these matrix effects.Furthermore high salt contents can cause physical interferences in the sample intro- duction system; the ion lenses are also considered to be impor- tant factors as they can lead to drift in the analytical values. As the salt content of the diet samples (25 ml) prepared from about 0.25 g of ash was 10 mg ml-l such samples must be diluted prior to analysis by ICP-MS. Therefore before meas- urements were made on the samples two checks concerning non-spectral interferences were conducted using one of the samples. The concentrations of the major and minor elements in the sample solution previously measured by ICP-AES,' were as follows Na 200 K 120 P 50 Ca 30 Mg 10 and Fe 0.4 pg ml-I. A range of matrix concentrations (100 250 500 700 and 1100 pg ml-l) were prepared by diluting the original solution (10 mg ml-I).Both Th and U were then added to the solutions to give a concentration of 10 ng ml-I and measured by an in- ternal standard method. The recovery of Th and U was good and in the range 96.8-103 and 98.2-106% respectively (shown in Fig. 1). The original concentrations of Th (15 pg ml-I) and U (300 pg ml-I) in the sample before spiking (as discussed in the next section and shown in Fig. 2) corresponded to 0.15 and 3.0% of the spiked 10 ng ml-' solutions respectively. The net recovery of Th and U ranged from 95.2 to 102%.The results showed the absence of matrix or other interferences at the 10 ng ml-1 concentration level. 1200 I I - E I A+ I D l I I I I 6 x-8 I I I Q U I I ox I 4. I " 60 70 80 90 100 110 120 Recovery of Th and U (%) Fig. 1 Effect of the total matrix concentration on the determination Th and U in solutions spiked with 10 ng ml-' of A 232Th; and B 23RU. Inter- nal standard Bi; n = 3 - E 1400 s .o 1000 600 CI m al ; 200 jx I%_ IX337 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. JUNE I99 1 VOL. 6 200 I ~~ 0 30 60 90 120 Measurement number Fig. 3 Drift of the z(wBi signal intensity during measurements on the diet samples for two examples A and B. The first 15 values were measured for the blank and standard solutions As another check matrix concentrations of 0 200,400,600 800 1000 1200 and 1400 pg ml-' were also prepared from the original diet solution (10 mg ml-I).After each sample had been analysed the concentrations of analytes were normalized to the analysed values of 1000 pg ml-I. The results are shown in Fig. 2. At matrix concentrations of 400-1200 pg ml-I both the Th and U concentrations found were almost constant ap- proximately 15 pg ml-I for Th and 300 pg ml-I for U. The con- centration of Th was one-twentieth that of U. At the upper and lower ends of the matrix concentration range tested the Th values found increased for a matrix concentration of 200 pg ml-' and decreased at 1400 pg ml-I. This behaviour might be due to the following the compensation provided by the in- ternal standard is insufficient the concentration of Th is near the detection limit or a large dilution factor was being used.From the above results the diet samples were measured by using ten-fold diluted solutions (a matrix concentration of 1000 pg ml-I). Drift in Analyte Signals Drift of the signal intensity for the elements during measure- ment of the diet samples was checked. Variations in the signal intensity of the '('Bi internal standard are shown in Fig. 3. The intensity is shown as the Bi count ratio for each sample rela- tive to that of the initial blank solution. Both suppression and enhancement of the analyte signals induced by concomitant matrix elements in the sample solu- tion have been reported." Suppression is seen as the usual pattern due to the matrix effects and is induced by a combina- tion of several mechanisms the contributions of which depend on the type of instrument employed and the operating condi- tions." The drift in the signal intensity was found to be 70% or greater over 120 measurements.One reason for the signal drift was the high viscosity of the sample solution because of the high matrix concentration (1000 pg ml-' of ash) which result- ed in clogging of the sample introduction system including the nebulizer and/or partial clogging of the sampling cones. It is considered that deposition of the matrix elements on the surface of the sampling and skimming cones the lenses etc. causes a change in the apparent potential in the region result- ing in enhancement or suppression as Crain et al." and Gre- goire" have reported.Significant deposition of salts on the extraction and collection lenses and the photon baffle was ob- served in the present experiments. Crain et a/." observed that signal suppression or enhancement was induced when the po- tential changes of the ion lens were negative and positive re- spectively. Therefore both positive and negative effects could be caused even by a similar composition of matrix elements as in the present results. The space charge effect was considered to be a major con- tributor to the matrix effect in previous work.* Variation of the potential in the interface region owing to the matrix however seems to be a more dominant factor. It is known that the kinetic energy of the ions depends on the mass; ions close in mass would have close kinetic energies.I4-l5 This is an important point when choosing the internal standard.From the study by Crain et a!.," it is suspected that a change in the kinetic energy of the ions would not be caused by the biological matrix for example Na K P and Ca ions in the diet samples. For the reasons mentioned above internal stan- dardization using Bi would be effective for both enhance- ment and suppression in determining Th and U in biological samples although drifts in the signal intensity of 70% or more occurred. Comparison of ICP-MS and Alpha-Spectrometry for U For one diet sample the 238U concentration was also deter- mined by alpha-spectrometry. The U concentration in ash ob- tained (0.29 f 0.05 pg g-I) showed good agreement with the result (0.30 f 0.01 pg g-') by ICP-MS.The total analysis times for the two methods are very different for example 2 weeks for alpha-spectrometry and a 2-3 d for ICP-MS starting with the diet ash. Furthermore the analytical procedure for ICP-MS is simpler than for alpha-spectrometry. The running costs and initial price of the instrument are the only disadvantage of ICP-MS. Concentration of Th and U in Diet Samples The mean concentration and standard deviation of Th in the ash of the diet samples was 25 k 12 ng g-I (n = 62) for 7.7- 72 ng g-l of ash. For U the results obtained were 4 4 f 20 ng g-' ( n = 62) for 18-93 ng g I of ash. Conclusion In the analysis of total diet sample solutions having fairly high matrix concentrations the effects of the matrix concentrations and the drift in the signals of the internal standard from the viewpoint of non-spectral interferences have been discussed.Thorium and U in diet samples with a total salt concentration of 1000 ng ml-I were easily determined by ICP-MS. In com- parison with alpha-spectrometry the samples were analysed without chemical separation and within a shorter time. The ICP-MS technique is very powerful and convenient for the de- termination of ultra-trace elements as chemical separation is not necessarily required. References Houk. R. S. and Thompson J. J. Mass Sprcw)m. Reis. 1988. 7 425. Gray A. L. Spectrochim. Actu. Part B. 1985,40 1525. Vanhoe H. Vandecasteele C. Versieck J. and Dams R. Anal. Chrm. 1989,61 1851. Yoshinaga J. Nakazawa. M. Suzuki. T. and Morita M. Anal. Sci.. 1989. 5. 355. Dean. J. R. Ebdon. L.. Crews H. and Massey. R. C. in Procvedings of the Inrer-nutionul Conjerewe of AnaIytic,al Applied Spec~rrnscupy~ eds. Creaser. C. S. and Davies A. M. C. The Royal Society of Chemistry London 1988 p. 305. Shiraishi K. McInroy. J. F.. and Igarashi Y.. J . Nuti-. Sri. C'itaminol. 1990,36 81. Shiraishi K. Yoshimizu K. Tanaka G.. and Kawamura H. Heultli Pliys. 1989 57 55 1. lgardshi Y. Kawamura H. Shiraishi K. and Takaku Y.. .I. A n d . At. Spec,tum. 1989. 4 57 1.338 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1991 VOL. 6 9 Radiotissue Chemistry Analytical Technique ed. Gautier M. A. Los Alamos National Laboratory Los Alamos NM 1987. 10 Gladney E. S.. Anal. Chim. Acra 1980 118 385. 1 1 Crain J. S. Houk R. S. and Smith F. G. Spectrochim. Acta Part B 13 Gregoire D. C. Appl. Spectrosc. 1987,41 897. 14 Thompson J. J. and Houk R. S. Appl. Spectrosc. 1987,41,801. 15 Fulford J. F. and Douglas D. J. Appl. Specrrosc. 1986,40,97 1. 1988,43 1355. Paper OlO3977B 12 Kim Y. S. Kawaguchi H.. Tanaka T. and Mizuike A. Spectro- Received September 3rd 1990 Accepted January 4th I991 chim. Acta Part B 1990,45 333.

ISSN:0267-9477    

DOI:10.1039/JA9910600335

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 1 VOL. 6 339 Suitability of Total Reflection X-ray Fluorescence Spectrometry for Elemental Speciation Studies S. Mukhtar and S. J. Haswell* School of Chemistry The University of Hull Hull HU6 7RX UK Total reflection X-ray fluorescence spectrometry (TXRF) has been shown to be applicable when determining differ- ent oxidation states in a variety of compounds by the method of KNKa intensity ratioing. It has also been shown that by using TXRF it is possible to relate shifts in the intensity ratio to coordination bonding. Keywords X-ray fluorescence; energy dispersive X-ray fluorescence spectrometry; total reflection X-ray fluorescence spectrometry; speciation Energy dispersive X-ray fluorescence (EDXRF) analysis is con- sidered a major technique for multi-element analysis of trace elements at ppm levels. Total reflection X-ray fluorescence spectrometry (TXRF) although based on an EDXRF-type de- tector has different instrumental geometry and offers sub-ppm levels of detection for a wide range of sample types.' The use of K a and KB X-ray fluorescence lines in EDXRF is important as they are used to determine intensities of unre- solved lines in deconvolution programs.Scofield? derived values for the relative line intensity ratios for KB and K a lines using theoretical models and some work has been carried out to determine Ka/KI3 values using energy dispersive detectors in conventional EDXRF geometry. The excitation sources used have been either radioactive sources3-10 or X-ray tubes.3.5.X.' I - 1 5 Much of the reported work dealt with either pure metals or their oxides3-lS and many of the workers reported discrepancies in their values compared with the theoretically predicted values of Scofield2.The deviation of the experimental values was attri- buted to the fact that the theoretical model used was not correct. In addition some workers attributed the deviation to the chemical environment of the analyte element.7,'3-'s A study by Brunner et al.I3 showed that the KB/Ka X-ray intensity ratio was sensitive to the chemical environment for 3d elements. The results obtained showed deviations in the KI3/Ka ratio of up to 4% between compounds and pure elements. A study of chemical effects on KI3/Ka X-ray intensity ratios in 3d ele- ments by Venkateswara Rao et al.I4 also reported deviations of up to 5% in compounds when compared with values obtained for pure elements.Tham and Preiss'I also found that KI3/Ka ratios of pure elements were significantly different from their compounds and suggested the following requirements for the study of KB/Ka intensity ratios ( a ) thin sample preparation to minimize both sample self attenuation of K a and KB X-rays statistical fluctuations in background scatter and sample prepa- ration; and ( h ) a system design that has reproducible (i) detec- tor-sample distance (ii) source-sample distance and (iii) detector-sample-source angles. The TXRF technique meets all the requirements suggested by Tham and Preiss. The aim of this work was to examine the use of TXRF for the measurement of KB/Ka ratios for various elements and also to study the variation of the KOKa ratio associated with 1 igand characteristics .Experimental Instrumentation Elemental determinations were carried out using an EXTRA I1 energy dispersive X-ray fluorescence spectrometer fitted with a multiple total reflection unit. The EXTRA I1 is equipped with a * To whom correspondence should be addressed. Rich Seifert ID 3000 high-voltage generator fitted with the ap- propriate control and regulation hardware. The X-ray tube voltage can be varied from 1 to 60 kV in steps of 1 kV while output currents from 1 to 80 mA in steps of 1 mA can be selected. The total reflection chamber has two reflector units one optimized for M e K and the other for W-white spectrum ra- diation.The two fine-focus X-ray tubes (SF60; K Mo and W as anode materials) have a maximum output of 2000 W and a line profile of 8 mm width and 0.4 rnm depth. The X-ray analyser was supplied by Link Analytical and consisted of an AN 10/55 analyser system. The Si(Li) energy dispersive detector crystal used had an active area of 80 mm and a resolution of < 155 eV at 5.9 keV. The detector was fitted with a pulsed optical feedback pre-amplifier and connected to a pulse processor equipped with dead-time correction and pulse pile-up rejection circuitry and a 100 MHz analogue to digital converter (ADC). The data handling system consisted of a 5 12 Kbyte CPU (20 MHz clock) two floppy disks and a single 20 Mbyte hard disk running software for auto-acquisition data processing and in- strument control.For this study only the Mo anode was used. All measurements were carried out at 50 kV with current in the range 10-38 mA. A Shimadzu UV-240 ultraviolet/visible recording spectro- photometer (Graphicord) was used for measuring molar ab- sorption coefficients. Reagents The following reagents were used CrC13-6H,0 ( AnalaR; Merck Poole Dorset UK) CrO (AnalaR; Merck) V,O (99%; Aldrich Gillingham Dorset UK) VOSO (99.9%; Aldrich) NaAsO ( AnalaR; Merck) Na,HAs04.7H,0 (AnalaR; Merck) CuC1 (Merck) Cu(CH,COJ ( AnalaR; Merck) CuBr (Hopkin and Williams London UK) Cu(HCO,) (Hopkin and Williams) and CuMeEDTA (EDTA = ethylenediaminetetraacetic acid) (J. Mendham Thames Poly- technic London UK). Stock solutions of 1000 ppm were used; all compounds were dissolved in distilled de-ionized water except for V,O which was made up in water with the pH adjusted to 12.1 using 0.5 mol dm-' NaOH (AnalaR) solution and VOSO which was made up in acidified water using 1 mol dm-' H,SO (AnalaR) to give a pH of 1.3.All solutions were diluted to 10 pprn for analy- sis by TXRF and to 250 ppm for molar absorption measure- ments. The Cu film was obtained by a sputtering process (courtesy of S. Pizzeani Strathclyde University Glasgow UK). Procedure A 10 p1 aliquot of a 10 ppm solution was transferred by pipette onto a siliconized quartz plate substrate and the plate was then340 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 I VOL. 6 Table 1 KB/Ka values for a variety of compounds KWKa Compound ratio sn- I t ftab RSD(%) n VZOS 0.1382 1.12 x 0.81 5 VOS04 0.1362 8.30 x lo4 0.61 4 Na,HAs04.7H,0 0.15 12 1.2 x lo-' 0.82 5 NaAsO 0.1429 1.5 x lo-' 0.98 5 CrCI3.6H20 0.1406 9.07 x 1W 0.32 4 cro 0.1430 2.98 x 0.84 5 Cu (metal) 0.1356 8.2 x 10-4 0.6 5 2.96 2.36 9.66 2.31 5.63 2.36 t-Tes t*- x - y n l n 2 t = - .- > t,* (95%; degreesof s2 n +n2 freedom = n l + n 2 - 2 ) (n - 1)s; f (n - l)S,* wheres2 = n + n - 2 * Reference 17. Table 2 Linearity of KB/Ka ratio as a function of mass x=KB/Ka inten- sity ratio for first oxidation state; y = KBKa intensity ratio for second oxi- dation state; s = standard deviation for x; s = standard deviation for y; n = number of replicates x; n = number of replicates y; s2 = pooled stan- dard deviation; t = calculated t-value; and ttab = t-value obtained from tables Parameter 25 ng 50 ng 100 ng s 0.1400 0.1394 0.1430 y 0.1369 0.1351 0.1369 s 3.5 x lo-? 2.56 x 2.98 x lo4 s 2.6 x lo-' 1.4 x lo-? 4.4 x 10-4 n 5 4 5 n2 4 4 4 s? 3.15 x lo-' 2.06 x lo-' 3.66 x lo-" t 1.47 2.95 24.84 t, 2.36 2.45 2.36 Table 3 sition of CrV1 and Cr"' Variation of KB/Ka ratio as a function of percentage compo- Composition of CrV1 (%) KB/Ka ratio n s,_~ RSD (%) 1 00 77 60 50 33 O* * 100% Cr"'.0.1430 5 2.98 x lo4 0.2 0.1426 5 7 . 1 6 ~ 1Q4 0.5 0.1424 5 4.87 x lo4 0.3 0.1426 5 8 . 4 0 ~ lo4 0.6 0.1418 5 4 . 8 7 ~ lo4 0.3 0.1406 4 9.07 x lo-' 0.6 dried under an infrared lamp. The plate was inserted into the spectrometer and counted for a time of either 500 or 1000 s. Linearity of the KB/Ka values was checked by using solutions containing 2.5 5 and 10 ppm which gave corresponding mass values of 25,50 and 100 ng respectively.Mixtures of oxidation states for single elements were also examined. In this study 5 ppm solutions of Crvl and Cr'll were used. The solutions were mixed in an Eppendorf vial to give compositions in the range from 100% Crvl to 100% Cr"'. The influence of the presence of a ligand on the KBKa in- tensity ratio for the coordinated element with a fixed oxidation state in this instance Cu" was examined. This work involved comparison of any variation observed with other chemical data such as molar absorption coefficients and apparent stability constants. Stability constant data were obtained from tables.'(' The molar absorption coefficient was measured on an ultravio- let/visible spectrophotometer using 250 ppm solutions and a path length of 1 cm at the wavelengths indicated in Table 4.Results and Discussion Oxidation State Studies In previous work of this type pure solid compounds or elements were used and hence owing to their physical state their chemistry remained constant. In this work solutions except for the copper film rather than direct solids were applied and dried on the quartz reflector for analysis. There- fore when preparing solutions for analysis it was important to ensure that parameters such as pH did not alter the species present e.g. AsV + As"' at pH c5. In addition because all the samples were dried using an infrared lamp it was important to be aware of compounds undergoing air oxidation. Data fQr the K13/Ka ratios were obtained through the windowing procedure in the manufacturer's software.Windows for each peak were selected through the keyboard and identified on the visual display unit (VDU) screen by defining a selected number of channels bordered by background on either side. Intensities for the KB/Ka peaks had the background subtracted from them making the assumption that the background was linear over the energy range of the window for each particular element/ compound analysed. It can be seen from Table 1 that the relative standard devia- tion (RSD) for n replicate determinations on the same solution is below 1% indicating that the sample methodology used is satisfactory and that some level of confidence can be placed on the ratio obtained. From the data in Table 1 the t-test shows that there is a significant difference (at the 5% level) between the two different oxidation states for all the elements studied (i.e.values greater than ttab). However the KOKa values in Table 2 show that at lower masses of Cr the precision suffers owing to the lack of sufficient counts in the Ki3 peak using a count time of 1000 s (i.e. at 25 ng). Applying a t-test to the values obtained for 25 ng of Cr"' and Crvl no significant dif- ference at the 5% level was found; this lack of discrimination between the two oxidation states can however be overcome by counting for a longer period of time. However for the other two masses ( i e . 50 and 100 ng) a significant difference was found at the 5% level using a t-test between the two different oxidation states. From Table 3 it can be seen that between the two extremes of 100% Crvl and 100% Cr"' for which there was a significant difference at the 5% level no difference for the mixtures could be identified using the t-test; therefore the clarity of this varia- tion cannot be identified by parametric tests.However by ap- plying cluster analysis (a non-parametric test) to the data it was found that some information could be obtained on the groupings of the various components of the mixtures. The den- drogram shown in Fig. 1 indicates groups A B and C. From the dendrogram it can be seen from the points of fusion that while groups A B and C are dissimilar group A is distinctly different from the other two. It can be concluded that on this basis although it might not be possible to determine mixtures accurately using parametric methods a general trend for the level of oxidation of an element in a sample can be obtained from techniques such as cluster analysis.Effect of Coordination Bonding It has been noted by various workers that the KB transition probability K-M,. i.e. 3d 3/2 5/2 can be significantlyJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. JUNE 199 1 VOL. 6 34 1 1 B i 100% Cr"' 100 60 77 50 33 0 100% Cr"' Cr composition (%) Fig. 1 of fusion Dendrogram for mixture\ of Cr"' and Cr". Circles indicate points Table 4 Comparison of KIJ/Ka values with molar absorption coe ffi c ie n t s and s t a bi 1 i t y constants Parameter CuBr CuClz Cu(HC( KWKa ratio 0.1254 0. I268 0.126 Molar absorption coefficient/ mol-' dm'cm-' 2.13" 2.03* 2.19-i- pH (250 ppm) 5.06 5.14 5.52 Stability con st ant (log x.) 0.32 0.66 1.57 Cu(CH,- CuMe- !).CO,) EDTA 0.1275 0.1288 3.883 7.71s 5.84 5.98 1.79 17.87 * At 8 10 nm. + A 794 nm. ri At 744 nm. Ei At 725 nm. ll Auuming that the value of CuMeEDTA is almoct the \ame as that of CuEDTA. Table 5 \tudied. r-Te\t at the 95% level Statiwcal \igniticant difterence\ between the Cu" compound\ Cu(CH;- CuBr CuCI Cu(HCO,) CO,) CuMeEDTA - CuBr S* NS? S S CUCI S - NS NS s Cu(HCO,) NS NS NS S - - Cu(CH,CO,) S NS NS NS CuMeEDTA S S S NS - * S = Significant difference. f NS = No qignificant difference. affected by the chemical environment.l.h.".'" The data in Table 4 show the effect of various ligands on the KOKa ratio as the ligand strength increases. These results might indicate that there is an apparent influence on the K13/Ka ratio associated with the chemical environment of the element. It is interesting to note that statistically the results suggest that there are two groups those consisting of inorganic ligands and those consist- ing of organic ligands (Table 5 ) .This suggests that the effects on the KBKa intensity ratio cannot be attributed to electrone- gative effects and are more probably due to ligand-field effects; it is known that Cu2+ forms distorted octahedral com- plexes.lx It was found that the molar absorption coefficient measurements also increased with ligand strength CuC1 being the exception in this respect perhaps due to a combination of parameters such as electronegative effects coupled with distor- tion of the axial bonds in the octahedral complex for CuBr,.In addition as the Br atom is larger than the C1 atom steric repul- sion might also have some effect in that the ligand-field split- ting would increase as the ligand strength increases. Conclusion It has been shown that TXRF can be applied to study changes in KBKa intensity ratios associated with elemental oxidation states and chemical environment. Stable oxidation states for V As and Cr can be statistically identified when present at 100% but investigations based on Cr suggest that the determination of mixed oxidation states can only be qualitative. The chemical environment of Cu when present with various inorganic and organic ligands has an effect on the KBKa ratios and can be used to indicate the presence of coordination bonding.It should be stressed that both these observations are essentially qualita- tive but serve to supplement information to a total elemental analysis which remains the major objective of TXRF analysis. The authors thank A. Walmsley for assistance with the cluster analysis. 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 18 17 References Prange A. Spec.trothim. Acta Part B 1989 44 437. Scofield J. H. Phys. Re\,. A. 1974 9 1041. Slivinsky. V. W.. and Ebert P. J. Phys. Re\'. A 1972,5 158 1 . Tamaki Y.. Omori T.. and Shiokawa T.. Rudiochem. Radioanal. Lett. 1975,20 255. Paic. G.. and Pecar V. Phys. Rei,. A 1976 14 2 190. Lazzanni. E. Lazzanni Fantola A.. and Mandelli Bettoni M. Radio- chim. A i m 1978 25. 8 1 . Tamaki Y Omori T. and Shiokawa T. Radiochem. Rudioanul.Lett. 1979.37 39. Venkateswara Rao N. Bhuloka Reddy S. Satyanarayana G. and Sastry D. L. Phy.Yic-a. 1986 138C 215. Venkateswara Rao N. Bhuloka Reddy. S. Satyanarayana G. and Sastry D. L. Physicw 1986 142C 375. Venkateswara Rao N. Sankara Rao Bh. Suryanayana Ch. Bhuloka Reddy S.. Satyanarayana G. and Sastry D. L. Port. Phys.. 1986 17 35. McCrary. J. H. Singman L. V.. Ziegler L. H. Looney L. D. Edmonds. C. M. and Harris. C. E. Phys. Rev. A 197 I 4 1745. Smith D. G. W. Reed S. J. B.. and Ware N. G. X-ray Spec'trom. 1974.3. 149. Brunner. G. Nagel. M.. Hartmann E. and Amdt E. J . Phy.r. B 1982,lS. 3517. Venkateswara Rao N. Bhuloka Reddy S. Raghavaiahi C. V. Ven- kataratnarn. S. and Sastry. D. L. Port. Phys.. 1986 17 143. Tham F. S.. and Preiss. I. L.,J. Anal. A f . Specworn. 1988. 3. 1127. Stability Constants Spec. Publ. No. 17 and 25 The Chemical Society. London 197 I . Nicholls D. Comple.t-es arid First-Rm' Ti.utisition Elements Macmil- lan. London and Basingstoke. 1st edn. 1974. Nalimov V. V. The Applic.utioti of Muthemutic,al Stutistir,s to Chemi- ( ~ r l Atia!\.si.s. Pergamon Press. Oxford. 1963 pp. 100 and 257. Puper 0/05399F Recei\>ed Noi9emher 29th I990 Accepted February 4 t h 1991

ISSN:0267-9477    

DOI:10.1039/JA9910600339

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1991 VOL. 6 CUMULATIVE AUTHOR INDEX Abell. Ian. 145 Abollino O. 1 19 Ali Abdalla H. 2 1 1 Andersen Knut-Jan 277 Apte S. C. 169 Barnes Ramon M. 57 Baxter Douglas C. 109 Beinrohr Ernest 33 307 Berglund Ingemar 109 Berman Shier S. 19 283 Blades Michael W. 215 Blais Jean-Simon 225 Blue James L. 261 Branch Simon 151 155 Bridenne Martine 49 Brindle Ian D. 129 Brindle Mary E. 129 Butcher David J. 9 Butler L. R. P. 329 Canals Antonio 139 Carbonell Vincente 233 Carre Martine 49 Chen Hengwu. 129 Chou Lei 273 Collins C. S. 329 Comber S. D. W. 169 Corns Warren T. 155 CsCmi Pavol 307 Dawson John B. 93 de la Guardia Miguel 233 de Loos-Vollebregt Diaz de Rodriguez Olga 49 Dittrich Klaus 3 13 Ebdon Les 15 I 155 Fang Zhaolun 179 30 1 Margaretha T.C. 165,323 FEBRUARY-JUNE 1991 Forbes Kimberely A. 57 Ford Mick 15 1 Foulkes Mike 15 1 Franks Jeff 145 Frech Wolfgang 109 Fuchs Holger 3 I3 Furata N. 199 Garden Louise M. 159 Gardener M. J. 169 Gervais Lyne S. 41 Gunn A. M. 169 Hassell D. Christian 105 Haswell S. J. 339 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 221 Julshamm Kaare 277 Kibble Helen A. B. 133 Kim Chang-Kyu 205 Kluckner Paul D. 37 Le Xia-chun 129 Ledingham Kenneth W. D.. 73 Littlejohn David 159 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 Mora Juan 139 Morita Shigemitsu 205 Mukhtar S. 339 Ng Kin C. 21 1 Offley Stephen G. 133 O’Neill Peter 151 155 Parsley David H. 289 Peng Runzhong 165 Poluzzi Vanes 33 Porta V. 119 Prell Laurie J. 25 Rademeyer Cor J. 329 Rapta Miroslav 33 Redfield David A. 25 Regnier Pierre 273 Reszke Edward E. 57 Rivikre Brigitte 3 13 Rowbottom William H. 123 Salin Eric D. 41 Salvador Amparo 233 Sampson Barry 115 Sanz Angel 233 Sarzanini C. 119 343 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. 26 1 Tye Chris 145 Tyson Julian F. 133 307 Uden Peter C. 57 Vanhoutte C. N. 323 Watters Robert L. Jr. 261 Welz Bernhard 179 295 301 Willie Scott N. 19 Winefordner James D. 21 1 Yamamoto Masayoshi 205 Yamasaki Shin-ichi 205 Yin Xuefeng 295 Yoshimizu Katsumi 335 Yu Li-Jian 261 Zachariadis George A. 239 Zeng Yun’e 22 1

ISSN:0267-9477    

DOI:10.1039/JA9910600343

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 199 1 VOL. 6 i 1991 Joint Meeting FA CSSlPacific Conference Agenda of Sessions and Registration Information Eighteenth Annual Conference of the Federation of Analytical Chemistry and Spectroscopy Societies and The Thirtieth Pacijic Conference on Chemistry and Spectroscopy October 6-11 1991 Disneyland Hotel and Convention Center Anaheim California The following four pages contain the agenda for the scientific sessions registration information for the meeting and a housing request form. rf you need more information please contact FACSS P.O. Box 278 Manhattan KS 66502-0003 (30 1)-846-479711 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1991 VOL. 6 1991 Joint FACSS/Pacific Conference Agenda Mondav AM *Challenges ofhalytical Toxicology *Recent Advances in Fourier Transform Raman *Supercritical Fluid chromatography H *Novel Methods for Characterization of Ceramics *Electrical Discharges Characterization and Utilization *Advances in Plasma Spectrometry *Sample Preparation and Digestion *New Techniques in Spectroscopic Imaging *Process Flow Injection Analysis I *NMR Imaging *Fourier Transform and Ion Trap Mass Spectrometry I "Environmental Analysis I "Resonance Ionization Mass Spectroscopy I spectroscopy I Tuesdav AM *SYMPOSIUM HONORING ARNOLD BECKMAN *Biological Analysis and Bioanalytical Developments *Array Detectors in Molecular Spectroscopy I *Supercritical Fluid chromatography *Novel Methods for Characterization of Electronic *Gas Chromatography *Diagnostics and Modelling of Plasma Sources I1 *The Graphite Furnace Fundamentals I1 *Optical Spectroscopy Using Diode Lasers I *Environmental Analysis I1 *NMR Techniques for Analyzing Solutions "Recent Developments in Bioinorganic Chemistry I *Fourier Transform and Ion Trap Mass Spectrometry I11 *ESR Techniques and NMR Spectroscopic *Automation and Process Control *Recent Developments in Main Group Chemistry *Flow Injection Techniques in Atomic Spectroscopy 50th Anniversary of the Beckman DU Materials Investigations of Sessions Mondav PM *m "Recent Advances in Fourier Transform Raman *Supe~ritical Fluid chromatography I1 *Novel Methods for Characterization of Ceramics *Analytical Approaches to ultratrace Analysis in *Diagnostics and Modelling of Plasma Sources I *Pmess Flow Injection Analysis I1 *Fourier Transform and Ion Trap Mass Spectrometry I1 *SOAP Two Decades of Developments "Resonance Ionization Mass Spectmscopy I1 *NMR Studies of Materials Chemistry & Processing The Graphite Furnace Fundamentals I *Novel Approaches in Environmental Monitoring "Surface Enhanced Raman Spectroscopy spemscopy I1 and Other Solids Biological Matrices "ICP optical spectroscopy Tuesdav PM *RSC ANALmCAL DIVISION SYMPOSIUM Atomic Spectroscopy *Biological Analysis New Approaches *Amy Detectors in Molecular Spectroscopy I1 *Ion Mobility Spectrometry *Novel Methods for Characterization of Catalysts *Signal Processing *GC Detecton *Diagnostics and Modelling of Plasma Sources I11 *Graphite Furnace Atomization *Optical Spectroscopy Using Diode Lasers 11 *Environmental Analysis I11 *Matrix Assisted Laser Desorption Mass Spectrometry *Recent Developments in Bioinorganic Chemistry I1 *Recent Developments in Organometallic Chemistry *POSTER SESSIONJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1991 VOL.6 ... 111 Wednesdav AM *ANACHEM AWARD SYMPOSIUM Awardee Ben Freiser Purdue Mass Spectmmetry and Ion/MolecuIe Chemistry I 'Bioanal ytical *Optical Fibers and Other Spectroscopic Developments *Environmental Applications of Chromatography I *Novel Methods for Characterization of Polymers *Detection Methods in Liquid Chromatography *Microcolumn Methods in Liquid Chromatography I *Signal Processing in Spectroscopy I *ICP-MS Instrumentation and Sample IntrPduction I *Recent Developments in Synthetic Organic Chemistry I "Current Trends in Bioorganic Chemistry I Trace Metal Precomntration Techniques *Nonlinear Optical Studies of Solids and Surfaces *Chemometrics Advances and Applications *Electrochemical Detectors and Sensors *Mass Spectrometry *Chemical Speciation "Forensic Chemistry Applications *Special Computer Poster Session Collection and Use of Fundamental Reference Data for Atomic Spectmscopy Thursdav AM *Proper Sample Handling with Today's IR Instruments I *Unconventional Vibrational Spectroscopy I *Capillary Electrophoresis I *Laboratory Automation Techniques I *X-ray Fluorescence I *Advances in Solids Elemental Analysis I *Computer Simulation of Chemical Systems I *Reactions at Surfaces I *Laser Ablation ICP-MS *Chemical Analysis of Single Cells *Near Infrared Techniques in Process Analysis *Physical Electmhemistry *New Tools for High Mass Analysis Electrospray and *Laboratory and Modeling Studies of Aerosol Matrix Assisted Laser Desorption I1 Chemistry and Physics Fridav AM *Novel Approaches in the IR and NIR Region "Reverse Phase HPLC and Ion Pair Chromatography *Laser-based Spectroscopic Techniques *ICP-MS and Glow Discharge-MS *Electroanalytical Biosensols and Modified Electrodes *Physical Chemistry Wednesdav PM "ANACHEM AWARD SYMPOSIUM Awardee Ben Freiser Purdue Mass Spectrometry and IorS(Mo1ecule Chemistry I1 "Industrial and Pharmaceutical Analysis *Remote Sampling with Vibrational Spectmscopy *Environmental Applications of Chromatography I1 *Special Topics in Materials and Surface Analysis *Spectroscopic Techniques in Process Analysis *Microcolumn Methods in Liquid Chromatography I1 *Signal Processing in Spectroscopy I1 *ICP-MS Instnunentation and Sample Introduction I1 *Recent Developments in Synthetic Organic Chemistry II *Current Trends in Bioorganic Chemistry I1 *Novel Plasma Devices for Atomic Spectmscopy *Supercomputers That Will Become PC's for 'Methods and Instrumentation in Electmhemistry *New Tools for High Mass Analysis Electrospray and *POSTER SESSION Chemical Analysis Matrix Assisted Laser Desorption I Thursdav PM __ ~~ *Proper Sample Handling with Today's IR Instruments I1 *Unconventional Vibrational Spectroscopy 11 *Capillary Electrophoresis 11 *Laboratory Automation Techniques I1 *Advances in Solids Elemental Analysis I1 *Computer Simulation of Chemical Systems I1 *Reactions at Surfaces I1 *Applications of ICP-MS *Nano-scale Spectmchemistq *Process Control and Applications of NIR in Quality *Spectroelectmchemistry *New Tools for High Mass Analysis Electrospray and *Kinetics and Spectroscopy of Atmospheric Trace *Novel Chromatographic Techniques *POSTER SESSION *x-ray Fluorescence I1 Control h e r Desorption Species 9 Fridav AM (co nt d) "Fourier Transform in Optical Spectroscopy *FT-IR Emission Spectroscopy A New/Old Tool for *ICP Instrumentation and Sample Introduction "Molecular Spectmscopy of Thin Films *Environmental Analysis The Atmosphere Spectroscopistsiv JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JUNE 1991 VOL.6 Housing Request Form October 6-11 1991 - Disneyland Hotel Anaheim W o d a Federation of Analytical Chemistry and Spectroscopy Societies == FACSS XVIII Paciac Conference on Chemistry and Spectroscopy and the Name First Name Initial Last Name Sharing Address First Name Last Name First Name Last Name Street Address City state Zip W e Country Phone Number Arrival Date Time Departure Date Credit Card Type Number Exp.Date Signature I PLEASE RESERVE ACCOMMODATIONS AS CIRCLED BELOW Towers Single .................................................................. $1 10 Twin/Double ....................................................... $120 Suites .................................................. Revailing Rate Children under 18 Free (Rates Effective October 3 through October 12) RESERVATIONS ARE TO BE MADE DIRECTLY WITH THE DISNEYIAND HOTEL DISNEYLANDHOTEL 1160 West Cenitog Avenue Phone (714) 956-6400 Anaheim CA 92802 FAX (714) 986-6582 If you register by phone or FAX please indicate that you are with the conference so you will receive the special rates with the hotel.If the category requested is no longer available the next available room category will be confirmed. Convention rates are available until September 1 199 1 * or until the block of rooms for the conference is filled. All resenrations are tentative until conflnned by a one night's deposit or guaranteed by a major credit card unless otherwise specifled. ADVANCE DEPOSITS ARE APPLIED TO YOUR LAST NIGHT'S STAY. We require 48 hours notice of an early departure to avoid a charge for that night. In addition a cancellation number must be issued by the hotel for refund of deposit or for release of guarantee no matter the cause for cancellation.I REGlSTRATlON FORM I V Federation of Analytical Chemistry & Spectroscopy Societies Pacific Conference Last Name (Pl- pint lqibly) F h Nme Middle Initial city SUtC zip phone Numba YOUR SCIENTIFIC SPECIALTIES (Enter Letter) Registration Fees Memberships oclnnuo 0 1.Preregistration (Deadline 9/16/91) 0 1. ACS Local A. Spectroscopy-General K. Solution Chemistry (check MC VISA only) ...... $80 Section Name B. Ultraviolet-Visible L. Electrochemical 0 2. Registration at conference c. Infrared- M. Chromatography-Thin Layer (cash check MC VISA).. $100 0 2. ACS Anal. Div. D. Mass Spectroscopy N. ChrmatographyGas 0 3. Single day registration ............. $60 0 3. SAS E. X-Ray 0. Chromatography-Liquid for (day 1 0 4.ANACHEM F. Emission-AA P. Thermal Analysis 0 4. Student full time ..................... $20 0 5. ISA G. Fluorescence Q. Computerization 0 5. Workshops (see fees below) ..... $- 0 6. DVCF H. Nuclear Chemistry R. proCessContro1 0 6. Spouse ....................... CompCimtntq 0 7. Coblentz I. ElectronOptics S. Gas Analysis 0 8. Royal Society J. NMR T. Other of Chemistry w m e e 0 7.FACSS Wed.GalaEvent ........ $45 0 8. Exhibits Only ........................... $10 9. Tours (see below) .......... $ YOUR PRXMARY RESPONSIBILITY Enter one number) 1. Research 4. Teaching 7. Service 2. Processing/QualityControl 5. Sales/Marketing 8. Student Total $ 3. Administration 6. Purchasing 9. Other Make checks payable to FACSS Credit card Number on 000 0110 oun 0 00 0 0 0 VISA (1 3 or 16 numbers) Master Card (16 numbers) Signature no nu MO YR Printed name as appears on card expiration date required ~ FACSSlPACIFIC CONFERENCE WORKSHOPS 0 A.Sample Preparation 0 B. Chemometrics 0 C. Lasers in Analysis D. OE. NearIR 0 F. Supercritical Fluid Chromatography Tours 0 1 . 0 2. Beckman Facilities...............,........................... $14 0 3. Monday October 7 Half Day .......................... $75 Monday October 7 Full Day ........................... $90 Monday October 7 Half Day .......................... $75 Professional Chemists In Industry Tuesday October 8 Full Day ......................... Free Tuesday October 8 Half Day .......................... $75 Tuesday October 8 Half Day .......................... $75 McDonnell Douglas (Space Shuttle) ................$14 Best of Hollywood and Beverly Hills ............... $25 0 G. 0 H. 0 I. OJ. 0 K. 0 L. 0 4. 0 5. 0 6. Bask Statistics Wednesday October 9 Full Day ............ $90 LCIMass Spectrometry Wednesday October 9 Half Day ............ $75 Optical Standardization Wednesday October 10 Half Day .......... $75 Analytical GC Thursday October 10 Full Day .............. $90 ICPrMS Thursday October 10 Half Day ............. $75 Robotics Thursday October 10 Half Day ............. $75 3. Paul Getty Museum .............................. $22 Orange County Beach Cities ................... $26 Huntington Library and Gardens ............. $40 Deadline for RECEIPT of Preregistration is September 16,1991 mail to FACSS P.O. Box 278 Manhattan KS 66502-0003Ramon M.Barnes Editor Department of Chemistry GRC Towers University of Massachusetts Amherst MA 01003-0035 Telephone (41 3) 545-2294 fax 545-4490 0 bjective The ICP INFORMATION 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 spectrochemical 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 TION 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 INFORMATION NEWSLETTER. Scope As the only authoritative monthly journal of its type the ICP INFORMA WON 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 INFORMA TION 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. Editorial 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 11-IV (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. Back issues 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 Cl Volume(s)- (June 19- - May 19- ) or 0 19 (January - December). Enclosed Prepayment 0 Check or money order OVISA 0 MasterCard Account No. (All 13 or 16 digits) D Purchase order (No. ) or 0 Send invoice. Date Cardholder Name Expiration date Cardholder Signature .Amount Due $ Mail to Name Organization Address City S t ate/Co u n t ry ZI P/Postalcode Telephone Telex/fax Note For each credit-card transaction a 3% service charge will be added reflecting our bank charges Current subscription rates are $60 (North America) $85 (Europe South America) or $94 (Africa Asia Indian/Pacific Ocean Areas Middle East and USSR). Back issue rates available on request. All payments should be made with US dollars by draft on a US bank by international money order or by credit card. Foreign bank checks are not accepted. Circle 003 for further information

ISSN:0267-9477    

DOI:10.1039/JA991060000i

出版商:RSC    

年代:1991

数据来源: RSC