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JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 93 Determination of Scandium Yttrium and Eight Rare Earth Elements in Silicate Rocks and Six New Geological Reference Materials by Simultaneous Multi-element Electrothermal Atomic Absorption Spectrometry With Zeeman-effect Background Correction* Joy G. Sen Gupta Geological Survey of Canada Ottawa Ontario Canada K 1A OE8 A method was developed for the simultaneous determination of a group of four rare earth elements (REE) in one firing using a multi-element graphite furnace atomic absorption spectrometer. The instrument can be programmed for automatic determination of an additional four REE elements in a second group by two firings. The sensitivities with a pyrolytic graphite coated graphite tube furnace are sufficiently high to permit the determination of low-pg g-I amounts of Y Nd and Sm and ng g-I amounts of Sc Eu Dy Ho Er Tm and Yb in silicate rocks from as little as 0.1 g or less of sample concentrate in a 1 ml final volume.After dissolution of the sample in acids Sc Y and the REE were preconcentrated by cation-exchange chromatography or coprecipitation with calcium oxalate and hydrated iron oxide carriers and determined by the proposed method. The interferences due to the presence of trace amounts of common metals in the ion-exchange concentrates were corrected for with Zeeman-effect background correction. Inter-method correlation plots for electrothermal atomic absorption spectrometry (ETAAS) versus inductively-coupled plasma mass spectrometry (ICP-MS) values and for oxalate versus ion-exchange recovery results for REE showed good agreement. Satisfactory results were obtained for Sc Y and eight REE in three international reference rocks MRG-1 SY-2 and NIM-G.The method was applied to the determination of these elements in six new candidate reference rocks of the Canadian Certified Reference Materials Project. In most instances the ETAAS results compared satisfactorily with those obtained independently by inductively coupled plasma atomic emission spectrometry (ICP-AES) and Keywords Scandium yttrium and rare earth element determination; silicate rocks and ores; multi-element electrothermal atomic absorption spectrometry; Zeeman-effect background correction; geological reference materials ICP-MS. There is a continuous need for scientists at the Geological Survey of Canada (GSC) to know the concentrations of yttrium and the rare earth elements (REE) in igneous mafic ultramafic and carbonate rocks for petrogenetic modelling.In most instances the lanthanide concentrations in these samples are so low that use of a preconcentration method and application of a highly sensitive instrumental technique are required to determine them. Neutron activa- t i ~ n ' - ~ stable isotope dilution mass spectrometry,6-8 spark- source mass spectrometry9-I3 and more recently direct current plasma emission spectr~metry,~~J~ inductively coupled plasma atomic emission spectrometry (ICP- AES)16-23 and inductively coupled plasma mass spectrome- try (ICP-MS)24-26 have been used with varying degrees of success.Other work in this area has involved the develop- ment of preconcentration of Sc Y and the REE by cation- exchange ~hromatography~~9~~ or by coprecipitation with calcium oxalate and hydrated iron oxide carrier^^^-^^ followed by determination using flame emi~sion,~~q~' flame atomic absorption spectrometry (AAS),28-33 optical emis- sion,31*33 electrothermal AAS (ETAAS)20~30-32-35 and ICP- AES.20 In the determination of Sc Y and the REE by ETAAS determination of only one element at a time rendered the process very laborious and time consuming. Moreover incompletely separated matrix elements after preconcentra- tion by ion exchange interfered in the determination of some elements; ash temperatures up to 2000°C and dilution of the concentrates were therefore recommended to eliminate these interference^.^^ In the proposed ETAAS *Presented in part at 74th Canadian Chemical Conference Hamilton Ontario June 2-6 199 1 .Government of Canada copyright reserved. Geological Survey of Canada Contribution No. 19092 method not only could four elements be determined in one firing and the instrument be programmed for the automatic determination of eight elements in two firings but also the interferences caused by the presence of associated impuri- ties in the concentrates obtained after ion-exchange separa- tion could be corrected for by Zeeman-effect background correction. The precision accuracy and speed of analysis were therefore greatly improved. The developed method was tested using reference ma- terials viz. Canada Centre for Energy and Mineral Techno- logy (CANMET) MRG-1 (Gabbro Rock) and SY-2 (Syenite Rock) and South African Bureau of Standards (SASS) SARM 1 NIM-G Granite with established REE contents and was then applied to the determination of SC Y and eight REE in six new candidate reference rocks and ores issued by the Canadian Certified Reference Materials Project (CCRMP).The results were compared with those obtained by ICP-AES and ICP-MS. Experimental Apparatus A Hitachi 2-9000 simultaneous multi-element atomic absorption spectrometer fitted with a pyrolytic graphite coated graphite tube furnace (part No. 190-6003) argon gas (UHP 99.999% exit pressure regulated to 44 lb in-2 and pre-dried by passing it through a Matheson Model 6406 gas purifier) and water (flow rate controlled at 1.5 1 min-' by a regulator) cooled to room temperature by mixing cold and hot water at the supply lines were used in all measurements.The built-in plotter of the 2-9000 instrument and an IBM- compatible PC were used for data recording. Before use a series of 12 borosilictte ion-exchange columns2* (each 30 cm x 1.8 cm i.d.) packed to a height of 15 cm with Dowex 50W-X8 cation-exchange resin (50-10094 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 mesh) were washed with 4 moll-' hydrochloric acid to free them from cations and then made neutral by washing with water. Reagents and Standard Solutions Ultra-pure water (ASTM Type I) and ACS-grade reagents were used throughout. Hydrochloric acid 1.7 and 4 mol 1-I. Nitric acid 2% vlv. Nitric acid 10% v/v-hydrogen peroxide 5% mixture.Bromophenol blue indicator solution 0.04%. Dissolve 40 mg of bromophenol blue in 100 ml of 95% ethanol and store in a tightly capped Nalgene bottle. Ammonium oxalate solution 0.1% mlv. Dissolve 1 g of ammonium oxalate in 1 1 of water and store in a plastic wash-bottle. Ammonium nitrate solution 1% mlv. Dissolve 10 g of ammonium nitrate in 1 1 of water and store in a plastic wash-bottle. A m mon ium eth ylenediam inetetraaceta te solution 0.8%. Weigh 4 g of ethylenediaminetetraacetic acid in a borosili- cate beaker add 100 ml of water and stir with gradual addition of sufficient ammonia solution until the solution becomes clear. Dilute to 500 ml with water and store in a plastic bottle. Methyl oxalate solution 40%. Dry oxalic acid crystals (COOH)2.2H20 in an air oven at 110 "C for several hours turning and breaking the lumps from time to time with a glass rod and exposing the crystals to heat to convert them completely into the anhydrous form.Cool grind to a powder and store in a stoppered bottle. Transfer 80 g of anhydrous oxalic acid into a 400 ml borosilicate beaker add 200 ml of methanol place the beaker on a medium hot- plate and stir with a glass rod to dissolve. Remove from the heat as soon as the solution becomes clear cool to room temperature and transfer into a stoppered bottle. Standard solutions of Sc Y and the REE 100 pg ml-I. Prepare by diluting 1000 pg ml-' Spex Industries plasma standard solutions (Sc Y La Ce Nd Sm Eu Gd Dy and Yb) and Johnson Matthey Chemicals Specpure standard solutions (Pr Tb Ho ER Tm and Lu) with 5% nitric acid.Prepare 100 ml of a stock synthetic standard solution of Sc Y and the REE only corresponding to the composition of 1 g ml-* of CANMET reference sample MRG-1 (based on the recommended values of Gladney and Roelandtsj6) by mixing aliquots of 1000 or 100 pg ml-l of the elements and diluting to 100 ml with 5% nitric acid (see Table 1 for composition). Prepare four working standard solutions of synthetic MRG- 1 having concentrations of sample equivalent to 0.05 0.10 0.15 and 0.20 g ml-l in terms of Sc Y and the lanthanides only by diluting 1 g ml-l of the above stock synthetic MRG-1 solution to appropriate volumes with 2% nitric acid. Store all standard solutions in tightly stoppered Nalgene bottles.Procedure Sample decomposition Weigh 1 g of the finely powdered and homogenized sample (-200 mesh) into a 100 ml Teflon beaker add a few drops of water and stir with a Teflon rod to make a slurry. Cautiously add (a small volume at a time) 10 ml each of concentrated nitric and hydrofluoric acids stir and quickly place a Teflon cover on the beaker to prevent loss due to vigorous exothermic reaction for some samples. Transfer to the groove of an iron hot-plate (or sand-bath) and evaporate nearly to dryness. Remove the beaker cool to room temperature add 10 ml each of concentrated hydrochloric and hydrofluoric acids and 2 ml of 70% perchloric acid and again evaporate nearly to dryness (avoid baking of the residue to prevent the formation of insoluble oxides). Repeat the evaporation process with an additional 10 ml of concentrated hydro- chloric acid.After cooling add 10 ml of concentrated hydrochloric acid 50 ml of water 5 ml of 0.8% ammonium ethylenedi- aminetetraacetate solution and dissolve the salts by stirring and heating on a hot-plate (or sand-bath). Filter the hot solution through a 9 cm Whatman No. 40 filter-paper and wash with hot 1 mol 1-l hydrochloric acid followed by water. Transfer any insoluble residue quantita- tively to the filter-paper using a rubber 'policeman' and a jet of water. Reserve the solution (filtrate A) transfer the residue into a 20 ml platinum crucible bum the paper in a mume furnace at 400 "C and finally heat to 800 "C to convert the salts into oxides. Cool the crucible to room temperature grind the residue to a fine powder with a round-tipped glass rod add 0.5 g of sodium carbonate and 0.1 g sodium peroxide and mix well.Place the covered crucible over a triangle enclosed by a chimney and fuse the mixture over a MCker burner at 1000 "C for 3-5 min. Remove the cover hold the tip of the crucible with platinum-tipped tongs and swirl the molten mass over the hot flame for complete decomposition of the residue then cool to room temperature. Cautiously add drops of concentrated hydrochloric acid and water to the crucible stir with a glass rod and warm on a hot-plate to dissolve the salts and loosen the cake. Transfer into a 20 ml beaker add more drops of concen- trated hydrochloric acid if necessary and warm on a hot- plate until dissolution of the salts is complete. Combine the solution with filtrate A dilute to 100 ml in a calibrated flask and store in a Nalgene bottle.Carry a blank through the above procedure for sample decomposition using the same amounts of acids and other reagents as for the sample. Preconcentration of Sc Y and the REE by ion-exchange separation Pipette 50 ml of the sample solution into a 100 ml borosili- cate beaker dilute to 80 ml with water mix well and pour into the ion-exchange column (a small volume at a time) and adjust the flow rate to 3 ml min-l. After the sample solution has passed through the column wash the beaker and the resin column with a total of 500 ml of 1.7 moll-' hydrochloric acid maintaining the flow rate the same as above. Discard the effluent. Elute the REE from the columns by washing with 650 ml of 4 mol 1-l hydrochloric acid at a flow rate of 4 ml min-l Table 1 corresponding to 1 g ml-'* Composition of a stock standard solution of synthetic MRG-I containing Sc Y and the REE only in concentrations Element Sc Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Concentration/pg ml-' 55 14 10 26 4 20 5 1.4 4 0.5 3 0.5 1.2 0.15 0.6 0.12 *See 'Recommended concentration' in ref. 36.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL.8 95 and collect the effluent in a clean 800 ml borosilicate beaker. Evaporate the solution to dryness overnight on a low hot- plate. Dissolve the REE salts by heating with 10 ml of concentrated hydrochloric acid and transfer into a 20 ml borosilicate beaker by rinsing with an additional 10 ml of hot concentrated hydrochloric acid.Evaporate the solution to dryness on a hot-plate. Dissolve the REE salts by briefly warming with 2 ml of 2% nitric acid transfer into a 5 ml calibrated flask by rinsing the beaker with the same acid and dilute to the mark. Transfer the solution into a 7 ml screw-capped plastic vial. Carry out a blank separation with 50ml of the blank solution using the same procedure as above. Preconcentration of Sc Y and the REE by coprecipitation with calcium oxalate and iron oxide carriers Transfer 1-5 g of the finely powdered and homogenized material (-200 mesh) into a 100 ml Teflon beaker and decompose the sample in the same way as above. (For a 3-5 g sample use 20 ml each of concentrated nitric and hydrofluoric acids for initial sample decomposition and subsequently evaporate with 5 ml of 70% perchloric acid for decomposition of fluorides and removal of hydrofluoric acid.) After evaporation with 70% perchloric acid dissolve the residue by heating with a mixture of 10% nitric acid and 5% hydrogen peroxide.When decomposition of the excess of hydrogen peroxide is completed allow any insoluble resi- due to settle and filter through an 11 cm Whatman No. 40 filter-paper collecting the filtrate in a 400 ml beaker. Wash the residue with hot 10% nitric acid-5% hydrogen peroxide mixture and then with water. Transfer the residue into a 30 ml platinum crucible ignite to oxide as usual in a muMe furnace and fuse with 1-3 g of sodium hydrogensulfate to a clear melt. After cooling dissolve the fused mass in hot water adding if necessary a few drops of 1 + 1 sulfuric acid to clear any turbidity.Combine this solution with the main solution add 200 mg of calcium (as nitrate) and a few drops of the bromophenol blue indicator and heat to boiling on a hot-plate. Cautiously add 15 ml of 40% methyl oxalate solution and neutralize with a freshly prepared concentrated ammonia solution until the colour changes from yellow to blue (pH 3.8-4.6) and a copious white oxalate precipitate separates out. Heat again to boiling on the hot-plate (unattended overheating in the presence of a substantial amount of the oxalate precipitate may cause bumping and loss of the material) transfer the covered beaker to a steam-bath and digest the solution for 2-3 h with occasional stirring and addition of a few drops of ammonia solution to restore the blue colour.Test the completeness of oxalate precipitation by adding a few drops of calcium nitrate solution (CaO approximately 100 mg ml-l). In the presence of an excess of methyl oxalate the immediate appearance of a white turbidity or precipitate is indicative of the completeness of precipita- tion. If the precipitate does not appear immediately add a further 1 ml of the same calcium nitrate solution and a few drops of ammonia solution to attain the blue colour stir well and allow the precipitate to settle overnight. Filter through a 9 cm Whatman No 40 filter-paper and wash the precipitate and the paper thoroughly with 0.1% ammonium oxalate solution. Transfer the paper with the precipitate to the original beaker cover and decompose by refluxing with 25 ml of concentrated nitric acid and 5 ml of 30% hydrogen peroxide.Evaporate the solution to dryness and repeat the refluxing with nitric acid and hydrogen Table 2 Instrumental parameters. Slit-width fixed at 0.8 nm in an Hitachi 2-9000 instrument Hollow cathode Wavelength/ lamp current/ Element nm mA sc Y Nd Sm Eu DY Ho Er Tm Yb 326.9 4 10.2 492.4 429.6 459.4 42 1.2 410.4 400.8 37 1.8 246.5 5.0 5.0 10.0 10.0 5.0 10.0 10.0 5.0 10.0 5.0 Table 3 Temperature programme for simultaneous determination of Nd Ho Er and Tm (group 1) and Y Sm and Eu (group 2) Temperature/"C No. Stage Start End Time/s 1 Dry 75 75 10 2 Dry 90 90 60 3 Dry 120 130 20 4 Ash 850 850 20 5 Ash 1400 1400 10 6 Atom 3000 3000 10 7 Clean 3000 3000 5 Monitoring stage 1-7 Carrier gas 200 ml min-l Interrupted gas 0 ml min-l Check stage 1-7 Table 4 Temperature programme for simultaneous determination of Sc Dy and Yb Temperature/"C No.Stage Start End Time/s 1 Dry 75 75 10 2 Dry 90 90 60 3 Dry 120 130 10 4 Ash 850 850 20 5 Ash 1400 1400 10 6 Atom 2600 2600 10 7 Clean 2800 2800 5 Monitoring stage 1-7 Carrier gas 200 ml min-l Interrupted gas 0 ml min-I Check stage 1-7 peroxide if necessary to remove any dark carbonaceous matter. Dissolve the residue in 1 mol 1-l nitric acid and reprecipitate the oxalates of Ca Sc Y and the REE by the same procedure as above. After filtration and destruction of the organic matter with nitric acid and hydrogen peroxide evaporate the solution to dryness. Dissolve the residue in 50 ml of 1 mol 1-1 nitric acid add 5 mg of iron as iron(iI1) nitrate and dilute to 100 ml.Add 1 g of hydroxylamine hydrochloride mix well heat to boiling and add freshly prepared ammonia solution until a brown iron(1rr) hydroxide precipitate separates out and the solu- tion smells of ammonia. Add a 10 ml excess of smmonia solution (pH> 10) and some analytical filter pulp then stir with a glass rod to disperse the pulp. Cover the beaker with a watch-glass and allow the precipitate and the pulp to settle for about 2 h with occasional stirring. Filter through an 11 cm Whatman No. 40 filter-paper and wash the precipitate and the paper thoroughly with 1%96 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 ammonium nitrate solution. Transfer the paper with the precipitate into the original beaker and destroy the organic matter by refluxing with concentrated nitric acid and 30% hydrogen peroxide as usual. Evaporate the solution to dryness dissolve the residue in hot dilute nitric acid transfer the solution quantitatively into a 20 ml borosilicate beaker and evaporate first on a hot- plate and then on a steam-bath to a moist residue. Add 2 ml of 2% nitric acid to the residue briefly warm the beaker on the steam-bath transfer the solution quanti- tatively into a 5 ml calibrated flask and dilute to volume with the rinsings of the same acid.Transfer the solution into a 7 ml screw-capped plastic vial. Determination of Sc Y Nd Sm EM Dy Ho Er Tm and Yb by mult i-elemen t E TAAS Determine these elements in a group of four or three from the ion-exchange concentrates and/or the concentrates obtained by coprecipitation with calcium oxalate and hydrated iron oxide carriers (final concentration of the sample solution=O.l g ml-I or less) by following the directions given under Instrumentation and Calibration.Instrumentation and Calibration The parameters used in this work to set up the instrument are given in Table 2. A temperature programme found satisfactory for Nd Ho Er and Tm (group 1) and Y Sm and Eu (group 2) is given in Table 3. An atomization tempera- ture of 2600 "C was used for simultaneous determination of Sc Dy and Yb (see Table 4). A tertiary wavelength (326.9 nm) and a secondary wavelength (246.5 nm) were chosen for Sc and Yb respectively because of the very high sensitivities of their primary lines with the pyrolytic graphite coated graphite furnace at the concentrations of solutions employed for preparing calibration graphs and for measuring most unknown samples.The determination of REE in most rock samples tested in this method worked satisfactorily with calibration graphs prepared from four synthetic MRG-1 solutions with con- centrations of 0.05-0.2 g ml-' as prepared above (see under Reagents and Standard Solutions). To prepare calibration graphs 30 pl each of four standard solutions of synthetic MRG- 1 with concentrations of 0.05-0.20 g ml-I (see Table 5 for concentrations of Nd Ho Er and Tm as Group 1 elements and Table 6 for concentrations of Y Sm and Eu as Group 2 elements) were transferred into the furnace by the autosampler (see Table 7 for the programme) and the elements were atomized using 0.40 0.30 0.20 0.10 0 0.801 (b' 1 o.20 L 4 0 1x103 2x103 3x103 4x103 0 60 120 180 240 a 2 0.40 < 0.30 0.20 0.10 0.55 0.45 0.35 0.25 0.15 0 25 50 75 100 0 7.5 15.0 22.5 30.0 Concentration/ng ml-' Fig.1 Calibration graphs for (a) Nd; (b) Er; (c) Ho; and (d) Tm at an atomization temperature of 3000 "C. Quadratic correlation Nd 0.9943; Er 0.9959; Ho 0.9970; and Tm 0.9975 the temperature programme in Table 3. From the calibra- tion graphs thus prepared (see Figs. 1 and 2) the concentra- tions of these elements in the unknown sample concentrate (final concentration 0.1 g ml-I or less) were determined by drying 10-40 pl of the solution followed by ashing and atomization using the temperature programme in Table 3.For the simultaneous determination of Sc Dy and Yb 20 pl of standard solutions (see Table 8) were transferred into the furnace by the autosampler and the elements were atomized using the temperature programme in Table 4. From the resulting calibration graphs (see Fig. 3) the concentrations of these elements in the unknown sample concentrate (0.1 g ml-I or less) were determined from 10-40 pl of solution. Results and Discussion Sensitivity The sensitivities for Sc Y Nd Sm Eu Dy Ho Er Tm and Yb as obtained at different temperatures using a pyrolytic graphite coated graphite tube furnace are given in Table 9. Previous valuesj5 for these elements determined using a similar type of furnace mostly at 2700 "C with a Varian single-element graphite tube atomizer (Model GTA-95) are also included in Table 9 for comparison.Table 9 shows that for some elements such as Sc Ho Er Tm and Yb the Hitachi 2-9000 multi-element instrument is either as sensitive as or more sensitive than the Varian GTA-95 instrument. The use of a higher temperature such as Table 5 Concentrations of Nd Ho Er and Tm (ng m1-I) in synthetic standard solutions for preparation of calibration graphs Element Standard 1* Standard 2 Standard 3 Standard 4 Standard 5 Nd 0 1000 2000 3000 4000 Ho 0 25 50 75 100 Er 0 60 120 180 240 Tm 0.0 7.5 15.0 22.5 30.0 *High-purity 2% nitric acid. Table 6 Concentrations of Y Sm and Eu (ng m1-I) in synthetic standard solutions for preparation of calibration graphs Element Standard 1* Standard 2 Standard 3 Standard 4 Standard 5 Y 0 700 1400 2100 2800 Sm 0 2 50 500 750 1000 Eu 0 70 140 210 280 *High-purity 2% nitric acid.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993.VOL. 8 97 Table 7 Autosampler programme Signal mode Measurement mode Standard replicate Sample replicate Sample volume Dilution Modifier add Cup position Cuvette Firings Result on record Chart speed Data communication Calculation (groups 1 and 2) Carrier gas interruption Optical temperature control Background corrected Calibration graph I or 2 1 o r 2 x pl* Off (sample) No 1 - Y t Pyro. 0 Yes (Concentration +Absorbance) 1 On Peak height for all elements Yes On *X= 30 pl for Nd Ho Er and Tm (group 1) and Y Sm and Eu t =Up to a maximum number of 72. (group 2); 20 pl for Sc Dy and Yb. 3000 "C is desirable in order to increase the sensitivities for the determination of Y and Nd to about 5 pg g-l and those of Sm Eu Ho Er and Tm to low-ng g-l levels in some rocks.The ability of the furnace in the 2-9000 instrument (a) 0.60 - 0.40 - 0 500 1000 1500 2000 0.25 - ( b ) 0.20 - 0 250 500 750 1000 0 50 100 150 Concentrationhg mi-' Fig. 2 Calibration graphs for (a) Y (b) Sm and (c) Eu at an atomization temperature of 3000 "C. Quadratic correlation Y 0.9926; Sm 0.9989; and Eu 0.9931 1.15 - (a) 0.92 - 0 5.5 11.00 0.15 - ( b ) 0.12 - I - I I I 0 0.20 0.40 0.60 0.75 - ( c ) 0.65 - 0.55 - 0.45 - 0 0.03 0.06 0.09 0.12 Concentrationhg mi-' Fig. 3 Calibration graphs for (a) Sc (b) Dy and (c) Yb at an atomization temperature of 2600 "C. Quadratic correlation Sc 0.9983; Dy 0.9991; Yb 0.9864 to tolerate continuously a high temperature of 3000 "C for 200 or more firings without change makes it ideally suitable for routine determinations of refractory elements such as Y and the REE.In previous s t u d i e ~ ~ ~ J ~ J ~ atomization tem- peratures of 2500-2700 "C were employed with pyrolytic graphite coated graphite tube furnaces to maintain their usefulness for longer periods as at repeated firings at higher temperatures they deteriorated rapidly. Applications The validity of the proposed multi-element ETAAS method was tested with three international reference rocks CANMET MRG-1 (Gabbro Rock) and SY-2 (Syenite Rock) and SARM 1 NIM-G (Granite) with established REE contents. The results in Table 10 show that in most instances the ETAAS values are either very close to or within the range of 'recommended' or 'usable' Fig.4 shows inter-method correlation plots for Nd Sm Ho Er and Tm comparing the ETAAS and ICP-MS results for some rock samples submitted by GSC scientists for petrogenetic modelling. In all five instances the data points fall near the 45" line demonstrating good agreement between the ETAAS and ICP-MS values. Using the autosampler the determination of four ele- values. 29,32,33,35-38 Table 8 Concentrations of Sc Dy and Yb (ng ml-I) in synthetic standard solutions for preparation of calibration graphs Element Standard I* Standard 2 Standard 3 Standard 4 Standard 5 sc 0.00 2.75 5.50 8.25 11.00 DY 0.00 0.15 0.30 0.45 0.60 Yb 0.00 0.03 0.06 0.09 0.12 *High-purity 2% nitric acid.98 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL.8 ETAAS Fig. 4 Inter-method correlation plots for ETAAS versus ICP-MS (a) Nd; (6) Sm; (c) Er; (d) Ho; and (e) Tm. Analyte concentrations inpgg-l Table 9 Sensitivities of Sc Y and REE elements as obtained with a pyrolytic graphite coated graphite tube furnace using the Hitachi 2-9000 simultaneous multi-element atomic absorption spectro- meter and comparison with some previous values Sensitivity*/pg Atomization This work with Previous values Element temperature/"C Hitachi 2-9000 with Varian GTA-95t s c Y Nd Sm Eu DY Ho Er Tm Yb 2600 2700 3000 2700 2800 2900 3000 2700 3000 2700 2 800 3000 2600 2700 2800 2700 2800 2900 3000 2 700 2800 2900 3000 2600 2700 2 800 2900 3000 2200 2600 423$ 480 4160 1900 1300 330 51 18 195 255 130 70 32 136 67 32 20 15 10 6 - - - - - - - - 3.81 1111 *Defined as the mass of the element in picograms that produces a change in absorbance compared with a pure solvent or blank of 0.0044.tSee ref. 35. $At 326.9 nm. §At 391.2 nm. 1At 398.8 nm. \/At 246.5 nm. 30 25 20 15 10 5 0 5 10 15 20 25 30 6 5 4 P) CI 4 3 B 2 1 0 1 2 3 4 5 6 1.5 - 0 0.5 1.0 1.5 2.0 Ion exchange Fig. 5 Inter-method correlation plots for oxalate versus ion- exchange preconcentration of Y and REE from CCRMP reference materials TDB- 1 WGB- 1 UMT- 1 WPR- 1 WMG- 1 and WMS- 1. (a) 0 Y; 0 Nd; and A Sm. (b) 0 Dy; 0 Er; and A Yb. (c) 0 Eu; 0 Ho; and A Tm. Analyte concentrations in pg g-'JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 99 Table 10 Determination of Sc Y and eight RE€ in MRG- 1 SY-2 and NIM-G by multi-element ETAAS after preconcentration by cation- exchange chromatography (results in pg g-l) MRG-1 (Gabbro Rock) SY-2 (Syenite Rock) NIM-G (Granite) This work* 50 14 Other values? 5 5 k 5 1 4 k 5 This work* 7.3 120 Other work 7.0 k 0.6-f 128k 17t 1201 ( 1 I 7 i25)ll 7 3 k 1 lt (8 1,84)11 i 6 + i t 171 2.4 k 0.3t 2 .3 ~ lo** 2in,ii 1 8 k 3 t 3.8 k 0.6t This work* 1 .o 113 Other work 0.5 -2.8$ 1154 80-187$ Element sc Y Nd 23 19.2 k 2.2 83 75 70** 43-83-43 14.6-2 1.5$ 0.3-2.2$ 15.4-17.2$ 68?tt 0.44,tt Sm Eu 5 1.8 4.5 k0.5 1.4 k 0.1 17 2.4 15 0.4 DY 3.5 2.9 k 0.9 21 16 Ho Er Tm Yb 0.6 1.4 0.2 0.8 0.5k0.01 1.1 k0.3 0.1 1 k0.05 0.6 4.0 13 2 18 3.4 11 2 17 3-5$ 3 ? t t 9.6-13.5$ l W t t 1.6-2.5$ 2**,tt 7- 16$ * Mean of two values.t 'Recommended concentration' in a compilation of data in ref. 36. $ See ref. 37. 4 See ref. 33. ISee ref. 29. 11 See ref. 32. **See ref. 35. tt'Usable value' reported in a compilation of data in ref. 38. Table 11 2-9000 spectrometer and comparison of results with those obtained by ICP-AES and ICP-MS (results in pg g-l) Determination of Sc Y and eight RE€ in three new CCRMP candidate reference rocks by multi-element ETAAS using a Hitachi Sample Element ETAAS (n) ICP-AES (n) ICP-MS (n) TDB-1 (Diabase Rock) sc Y Nd Sm EU DY Ho Er Tm Yb 33 36 2 3 k 5 (4) 2 7 k 1.6 (6) 9.3 k 1.7 (6) 1.9k0.1 (8) 5.5 5.7 0.93 0.97 2.8 k 0.2 (6) 0.34k0.02 (10) 2.5 2.5 33 30 26 k 5 (6) 6.4k0.7 (6) 5.8k0.5 (7) 1.10k0.22 (6) 0.39 k 0.13 (6) 23 k 5.7 (6) 1.9k0.3 (6) 3.2 k 0.7 (6) 2.9 k 0.6 - 31 k4.5 (1 1) 6.8 k 0.4 (1 1) 1.9k0.1 (11) 6.4k0.4(11) 26k2.2 (9) - - 2.9k0.5 (1 1) WGB-1 (Gabbro Rock) sc Y Nd Sm EU DY Ho Er Tm Yb s c Y Nd Sm Eu DY Ho Er Tm Yb UMT-1 (Ultramafic Rock) 30 34 1 8 k 1.6 (4) 1 5 2 2 (6) 3.4k0.9 (6) 1.3k0.16 (4) 2.8k0.2 (4) 0.46 0.47 1.4k0.5 (3) 0.22k0.10 (5) 1.4k0.1 (4) - 14k3.3 1 3 k 1 2.7k0.2 (6) 1.3k0.10 (1 1) 2.8k0.2 (11) 30 33 14k3.5 11 k 3.4 2.6 k 0.7 (6) 1.3k0.50 (6) 2.6 k 0.5 (6) 0.5 1 k 0.09 (6) 0.20 k 0.02 (6) 1.5k0.3 (6) 1.5k0.3 (6) 14 18 3.3k 1.1 (6) 1.3k0.4 (6) 0.35 k 0.12 (4) 1.3k0.5 (6) 0.26 2 0.06 (6) 0.8k0.2 (6) 0.10+0.03 (6) 0.8 20.2 (6) 6.5k2.5 (6) - 1.4k0.1 (11) 14 16 9.5 k 1.6 (4) 1.3 k0.2 (6) 0.32 k 0.04 (6) 1.8 k 0.3 (4) 0.23 0.20 5 k0.8 (6) 0.8 k 0.2 (8) 0.9 k 0.2 (4) 0.10 k 0.02 (8) - 6.5k0.6 (1 1) 5k0.9 (1 1) 1.3k0.2 (11) 1.5k0.2 (11) 0.35 k 0.03 (1 1) - - 0.7kO.l (11) ments in approximately 100 or more sample solutions could be completed per day.1 (Diabase Rock) WGB- 1 (Gabbro Rock) UMT- 1 (Ultra- mafic Ore Tailings) WPR- 1 (Peridotite Rock) WMG- 1 (Mineralized Gabbro) and WMS- 1 (Massive Sulfide Min- eral) were carried out using the proposed multi-element ETAAS method and by ICP-AES and ICP-MS. Determination of Sc y and eight REE in Six new CcRMp reference materials Determinations of Sc Y Nd Sm Eu Dy Ho Er Tm and Yb in six CCRMP candidate reference materials viz. TDB- Before determination the preconcentration of Sc Y and the REE was done mostly from replicate sample solutions100 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 ~ Table 12 Determination of Sc Y and eight REE in three new CCRMP candidate reference rocks by multi-element ETAAS using a Hitachi 2-9000 spectrometer and comparison of results obtained by ICP-AES and ICP-MS (results in pg g-l) Sample Element ETAAS ( n ) ICP-AES (n) ICP-MS ( n ) WPR-1 (Peridotite) sc Y Nd Sm Eu DY Ho Er Tm Yb sc Y Nd Sm Eu DY Ho Er Tm Yb s c Y Nd Sm Eu DY Ho Er Tm Yb WMG-1 (Mineralized Gabbro) WMS-1 (Massive Sulfide Mineral) 10 6 9 8 5.5 f 3.7 (4) I .5 f 0.9 (4) 0.3 0.3 1.8 1.5 0.13 0.1 1 0.55 k 0.20 (4) 0.57 f 0.02 (6) 0.13 0.16 20 21 13 12 12k4.5 (6) 2.9 2.9 0.8 0.9 3.2 3.2 0.40 0.43 1.3f0.45 (5) 0.2 f 0.04 (5) 1.6k0.2 (4) 1.8 1.3 5.9 5.0 4.3f1.1 (7) 0.6 f 0.1 (4) 0.1 0.1 0.7 0.8 0.08 k 0.0 1 (5) 0.06 f 0.01 (4) 0.31 k0.03 (7) 0.30k0.04 (6) - 8.4 4.2 4.7 f 0.3 (9) 5.92 1.4 (7) 1 .o f 0.2 (9) 0.3 k 0.05 (9) 1.3 k 0.4 (9) 4.7f2.1 (4) 2.7k 1 (4) 1.0k0.3 (4) 0.28 f 0.14 (4) 1.2 2 0.9 (4) - 0.18 k 0.04 (4) - 0.54 k 0.17 (4) - 0.07 2 0.02 (4) 0.50k0.10 (9) 0.50+-0.20 (4) - 21,21 1 2 f 1 (9) 122 1.8 (8) 11 f 1 (7) 9k0.4 (7) 2.8f0.2 (10) 2.4 f 0.2 (8) 0.74 2 0.03 (9) 0.71 k0.03 (8) 2.3f0.1 (9) 2.3k0.13 (8) - 0.48 k 0.03 (8) - 0.2 k 0.02 (8) - 1.1 k0.3 (8) 1.1 k0.2 (9) 1.220.2 (8) - 1.4 1.0 2k0.2 (9) 3.82 1.1 (6) 1.9k0.3 (9) 0.6k0.1 (6) 0.5 kO.l (9) 0.14 f 0.04 (9) 0.44fO.l (9) 0.4k 0.1 (9) 2.1 k 0.6 (9) 0.1 1 k 0.02 (9) 0.08 k 0.0 1 (9) 0.24k0.04 (9) 0.03 2 0.0 1 (9) 0.25 f 0.07 (9) - - - 0.23 f 0.04 (9) using an ion-exchange separation procedure.Also from some duplicate sample solutions preconcentration of these elements was performed using the calcium oxalate and hydrated iron oxide coprecipitation technique.As observed previously with some USGS reference rocks and CCRMP iron-formation reference materials,** satisfactory agree- ment was also found in this work between the results of these two sets of concentrates for Y and REE in the six new CCRMP candidate reference rocks (see Fig. 5 for inter- method correlation plots for oxalate versus ion-exchange preconcentration where most of the data points fall near the 45" line). The results for Sc Y and eight REE in the six new CCRMP reference samples (with 95% confidence limits where sufficient data were available) as obtained by ETAAS ICP-AES and ICP-MS methods on the same solutions (ion-exchange and/or oxalate preconcentrates) by three independent operators at the GSC laboratories are given in Tables 11 and 12.If the differences in the analytical mode used are considered (e.g. preconcentration procedure sample volume dilution calibration graph interferences final measurement technique and indepen- dent operator) the differences in results for high Y Nd and Sm concentrations in some samples such as TDB-1 and WGB-1 by the three methods appear to be minor. In most other instances the results are found to be of similar magnitude. Conclusions The determination of Sc Y and eight REE in geological materials using a multi-element graphite furnace atomic absorption spectrometer equipped with a Zeeman-effect background corrector and a large autosampler disc (capa- city 72 samples per run) is faster and more accurate than with a conventional single-element instrument without such background correction.The results are comparable to those of other instrumental techniques such as ICP-AES and ICP-MS. As the method is highly sensitive and usable with as little as 10-40 pl sample solution it is ideally suited for samples with very low REE contents and/or available only in small amounts. The proposed method has been in use in the GSC for about 18 months as an inexpensive procedure for the determination not only of trace and ultra-trace amounts of Sc Y and REE in geological materials but also of groups of other elements such as noble metals in rocks and metallurgical samplesJ9 and Li Cd Pb and Sb in rocks and environmental samples.4o The author is indebted to the coordinator of CCRMP for supplying the six new candidate reference materials used in this work and to his colleagues R.A. Meeds and N. B. Bertrand for determining Y and REE in them by ICP-AES and ICP-MS respectively. References 1 Haskin L. A. Wildeman T. R. and Haskin M. A. J. Radioanal. Chem. 1968 1 337. 2 Rey P. Wakita H. and Schmitt R. A. Anal. Chim. Acta 1970 51 163. 3 Roelandts I. Geostand. Newsl. 1977 1 7. 4 Brunfelt A. O. Roelandts I. and Steinnes E. Analyst 1974 99 277. 5 Kantipuly C. J. and Westland A. D. Talanta 1988 35 1.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 101 6 Schnetzler C. C. Thomas H. H. and Philpotts J. A. Anal. Chem. 1967,39 1988. 7 Hooker P. J. O’Nions R. K. and Pankhurst R. J. Chem. Geol. 1975 16 189.8 Hanson G. N. Natl. Bur. Stand. (US) Spec. Publ. 1976 No. 422 937. 9 Graham A. L. and Nicholls G. D. Geochim. Cosmochim. Acta 1969 33 555. 10 Strelow F. W. E. and Jackson P. F. S. Anal. Chem. 1974,46 148. 11 Rankin P. C. J. Geol. SOC. Jpn. 1976 82 215. 12 Taylor S. R. and Gorton M. P. Geochim. Cosmochim. Acta 1977,41 1375. 13 McLennan S. M. and Taylor S. R. Chem. Geol. 1980 29 333. 14 Feigenson M. D. and Cam M. J. Chem. Geol. 1985,51 19. 15 Flavelle F. and Westland A. D. Talanta 1986 33 445. 16 Walsh J. N. Buckley F. and Barker J. Chem. Geol. 1981 33 141. 17 Church S. Geostand. Newsl. 1981 5 133. 18 Buchanan S. J. and Dale L. S. Spectrochim. Acta Part B 1986 41 237. 19 Govindaraju K. and Mevelle G. J. Anal. At. Spectrom. 1987 2 615. 20 Sen Gupta J. G. Talanta 1987 34 1043. 21 Jarvis K. E. and Jarvis I. Geostand. Newsl. 1988 12 1. 22 Watkins P. J. and Nolan J. Geostand. Newsl. 1990 14 11. 23 Roelandts I. Spectrochim. Acta Part B 1991 46 79. 24 Riddle C. Vander Voet A. and Doherty W. Geostand. N e d 1988 12 203. 25 Jarvis K. J. Anal. At. Spectrom. 1989 4 563. 26 Doherty W. Spectrochim. Acta Part B 1989 44 263. 27 Hughson M. R. and Sen Gupta J. G. Am. Mineral. 1964,49 937. 28 Sen Gupta J. G. Tulunta 1984 31 1045. 29 Sen Gupta J. G. Talanta 1976 23 343. 30 Sen Gupta J. G. Anal. Chim. Acta 1982 138 295. 31 Sen Gupta J. G. Geostand. Newsl. 1977 1 149. 32 Sen Gupta J. G. Talanta 1981 28 31. 33 Sen Gupta J. G. Geostand. Newsl. 1982 6 241. 34 Sen Gupta J. G. Talanta 1984 31 1053. 35 Sen Gupta J. G. Talanta 1985 32 1. 36 Gladney E. S. and Roelandts I. Geostand. Newsl. 1990 14 373. 37 Steele T. W. Wilson A. Goudvis R. Ellis P. J. and Radford A. J. Geostand. Newsl. 1978 2 71. 38 Abbey S. Geol. Surv. Can. Pap. 1983 No. 83-15. 39 Sen Gupta J. G. Talanta in the press. 40 Sen Gupta J. G. in preparation. Paper 2/03805F Received July 16 I992 Accepted September 24 1992

ISSN:0267-9477    

DOI:10.1039/JA9930800093

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 103 Rapid Furnace Programmes for the Slurry-Electrothermal Atomic Absorption Spectrometric Determination of Chromium Lead and Copper in Diatomaceous Earth lgnacio Lopez Garcia Jesus Arroyo Cortez and Manuel Hernandez Cordoba" Department of Analytical Chemistry Faculty of Chemistry University of Murcia 30071 -Murcia Spain The samples are suspended in water containing hydrofluoric acid and then injected into the electrothermal atomizer. To decrease the heating programme time the drying step is performed at higher than usual temperatures and ashing and clean-up steps are omitted. Simple aqueous standards are used for calibration. The results reveal no significant differences at the 95% confidence level (Wilcoxon T-test and use of regression lines) from those obtained using acid digestion of the samples.The analysis of certified reference materials shows the reliability of the approach. The use of hydrofluoric acid solutions as the suspending media is confirmed to be a reliable way of prolonging the lifetime of platforms and tubes when slurries prepared from samples with a high silica content are used. Keywords Chromium lead and copper determination; diatomaceous earth; slurry; hydrofluoric acid; electrothermal atomic absorption spectrometry The application of electrothermal atomic absorption spec- trometry (ETAAS) to the direct analysis of solid samples without previous dissolution steps has attracted the inter- est of a number of researchers.' Although the two different approaches that can be used for this purpose namely direct solid and slurry introduction show interesting advantages over the conventional dissolution based methodology the use of suspensions has aroused increasing interest as it combines the advantages of both liquid and solid sampl- ing.2 These approaches are not free of problems and even if the essential condition of a low particle size can be met the procedures must be optimized to overcome the drawbacks arising from the direct introduction into the atomizer of certain types of matrices. For samples with a very high silica content a problem lies in the rapid deterioration of the graphite as a consequence of chemical attack when the heating programmes are run.3 This effect can be minimized by adding graphite p ~ w d e r .~ - ~ Recently Bendicho and de Loos-Vollebregt' reported a detailed study on the analysis of glass based on the preparation of slurries in a hydro- fluoric acid medium thus avoiding the deleterious effect and considerably enlarging the lifetime of the graphite platforms. As far as is known this simple interesting alternative has not been further developed for other materials with high silica content. Hallss showed several years ago that in some instances steps which are included in the conventional furnace programmes can be omitted or adequately modified thus considerably shortening the programme time. This methodo- logy has been applied to a variety of samples9-13 and extended to the use of suspensions. Thus Bradshaw and Slavin14 reported fast programmes for the slurry-ETAAS analysis of coal and fly ash samples.Bendicho and de Loos-Vollebregt made use of this approach for their studies on the analysis of glass7J5 and Hinds et all6 have also reported a study on the determination of lead in soils with excellent results. In this paper the determination of chromium lead and copper in diatomaceous earth (DE) a material with high silica content which has a number of industrial applica- tions is reported. As DE is extensively used as a filter aid and filler the determination of traces of metallic impuri- ties is of interest for quality control purposes. The charac- teristics of such a matrix permit the application of fast furnace methodology which considerably decreases the *To whom correspondence should be addressed.duration of the furnace programme. The use of hydrofluoric acid solutions as the suspending media is confirmed as increasing the lifetime of the tubes and platforms. Experimental Apparatus All measurements were obtained with a Perkin-Elmer Model 1 1 OOB atomic absorption spectrometer equipped with deuterium-arc background correction and an HGA- 400 electrothermal atomizer. Argon was used as the inert gas at 300 ml min-' except in the atomization step where the flow was automatically stopped by the software at - 5 s. The measurements were made using conventional hollow cathode lamps. Pyrolytic graphite coated graphite tubes (Cr and Cu determinations) and pyrolytic graphite platforms inserted into pyrolytic graphite coated graphite tubes with grooves (Pb determinations) were obtained from Perkin- Elmer (Parts B013-5653 and B012-1092 respectively).Background-corrected integrated absorbance was used as the analytical signal. A Branson Model 5 ultrasonic bath of 14 W constant power was also used. Reagents and Materials Doubly distilled water was used throughout. Hydrofluoric and nitric acids were obtained from Fluka. Stock solutions of chromium lead and copper (1000 mg dm-3) were obtained from Panreac (Spain). As recommended else- where,9 micropipette tips were cleaned before use by first pipetting 20% v/v nitric acid (twice) and then doubly distilled water (twice). A similar precaution against contam- ination was used for all the plastic and glass calibrated wear. Procedures Commercially available DE samples were ground for 10 min using an agate ball mill. The ground samples passed entirely through the 30 pm sieve.Slurries were prepared by weighing different amounts of the material (20-1250 mg) in 50 ml plastic containers. Then 25 ml of a hydrofluoric acid solution were added. The concentration of the acid was dependent on the percentage of the slurry. For 1% suspen- sions a 3% hydrofluoric acid solution was used. The suspension was submitted to ultrasound for 5 min. Next while the suspension was being magnetically stirred 10-25104 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 Table 1 Instrumental conditions for the determination of lead chromium and copper Wavelengthhm HCL current/mA Slit-widthhm 0.7 Chemical modifier None 283.3 (Pb) 357.9 (Cr) and 324.8 (Cu) 10 (Pb) 10* (Cr) and 15 (Cu) Furnace programme- Temperaturet/"C Step Pb Cr c u Ramp timeis Hold time/s Other setting - Dry 400 200 200 1 15 Atomize 1700 2600 2500 0 3 Stop flow read *Lamp current was reduced to achieve energy balance with the deuterium arc.?All temperatures quoted are values set on the HGA-400 power supply. pl aliquots were taken injected into the furnace and the heating programme given in Table 1 was run. Calibration was performed using aqueous standards. All measurements were made in integrated absorbance mode. Certified reference materials (CRMs) were analysed in the same way the samples being previously ground for 30 min. For comparison purposes DE samples (50- 1000 mg) were dissolved using nitric and then hydrofluoric acid in a platinum crucible.The solutions were made up to 25 ml with 0.1% nitric acid and the contents of chromium lead and copper determined. Measurement of a blank was performed in order to correct the results. Results and Discussion Preliminary experiments were performed using 0.2% sus- pensions prepared from DE in a 0.1% v/v nitric acid medium. The suspensions were introduced into the elec- trothermal atomizer and the signal due to the atomization of lead from a platform was obtained using a conventional heating programme (ashing at 900 "C for 15 s and atomizing at 2000 "C for 4 s using maximum heating power and ammonium phosphate as chemical modifier). The inte- grated absorbance thus obtained was repeatable only for the first injections When more than 40 successive injections were performed a noticeable decrease in the repeatability was apparent.Visual inspection of the atomization device revealed a serious deterioration of the platform. The damage was so severe that after about 60 injections the platform became detached from the grooves. When 5% suspensions were injected on a new platform this was completely pierced after only five runs. The deterioration of the pyrolytic graphite surface suffered when materials with high silica content are atomized has been reported3J7 as probably being due to the formation of silicon carbide resulting from chemical attack at the atomization tempera- ture. To overcome this drawback which in practice seriously limits the use of concentrated suspensions pre- pared from DE the addition of hydrofluoric acid to the suspension media was tested an approach which has already been reported by Bendicho and de Loos-Vollebregt7 for the analysis of glass.To check that the addition of hydrofluoric acid to the suspension media avoids the deleterious effect of the silicon when introduced into the furnace three suspensions with 0.5 1 and 5% of DE were prepared using hydrofluoric acid concentrations in the suspending media of 1 3 and lo% respectively. Sixty injections of each suspension were carried out using the above programme for lead atomiza- tion with a new platform for each suspension. No apprecia- ble deterioration of the platforms or of the repeatability were noted. Furthermore using a new platform 300 injections of the 1% suspension were performed with no apparent deterioration.From this it was concluded that the addition of hydrofluoric acid is a safe way of considerably increasing the lifetime of the platforms. Similar conclusions were drawn from another similar set of experiments using wall atomization. Diatomaceous earth samples are commercialized as powders with low particle size. To assess how low the particle size was suspensions were prepared and aliquots were taken and examined using optical and electron microscopy. The observations indicated that a notable fraction of the particles was in the 30-80 pm range. To check the influence of particle size on the analytical measurements slurries were prepared from samples that were ground for different times with an agate ball mill and the integrated absorbance from the atomization of lead obtained.For a 5 min grinding time the analytical signal was 10% higher than that obtained from unground samples. Further increases in the grinding time had no effect on the integrated absorbance. A grinding time of 10 min is recommended to ensure homogeneity and a low particle size. Under this condition the whole sample passed through the 30 pm sieve and the examination of the micrographs proved that about 95% of the particles were below 5 pm. It has been provedI4J8-l9 that in some situations where external appearance indicates that the analyte is being exclusively supplied to the atomizer as a slurry a consider- able fraction is in fact in the supernatant. This is due to an extraction process from the solid matrix as a consequence of ultrasonic treatment or of the solubilizing action of the suspension media.A number of experiments were carried out to clarify the solubilization effect due to the action of hydrofluoric acid on the slurries prepared from DE. For this the loss of mass of the solid fraction of the slurry was studied. Suspensions (1%) in pure water were prepared and submitted to ultrasound for 5 min. While the suspensions were being magnetically stirred 2 ml aliquots were taken and filtered through chromatographic 0.45 pm membrane filters. The filters were dried and weighed. Then concen- trated hydrofluoric acid was added to the suspension and aliquots were taken at different times and submitted to the same treatment. The results for three different concentra- tions of hydrofluoric acid are given in Fig.l(a) as the fraction of the solid mass still remaining in the suspension. The same methodology was followed to study the extent to which lead chromium and copper were solubilized by the hydrofluoric acid. For this the solutions that passed through the chromatographic filters were analysed for the three analytes and the integrated absorbance values ob- tained were ratioed with those obtained by injecting aliquots of the same slurry into the furnace. As the integrated absorbance was the same irrespective of whetherJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 105 the analyte was injected as a liquid or as a slurry this ratio was considered to be an indication of the fraction of the determinant extracted from the solid matrix.Assuming the solid sample is homogeneous these data should coincide with the mass loss curves. However as can be seen in Fig. l(b) which reports the results obtained for the measure- ment of lead there was no full agreement between the two sets of experiments and the extraction into the liquid phase increased faster than the loss of mass. This difference might be due to a non-homogeneous distribution of the analyte within the solid particles the presence of soluble com- pounds of lead or particles with a very low size which passed through the filter. Similar results were found for copper and chromium. Additional experiments were performed by injecting into the furnace 0.1 O/o suspensions prepared in 0.3% hydrofluoric acid and measuring the integrated absorbance due to silicon.To reduce the sensitivity the 288.2 line of silicon was used and the flow of argon gas was not stopped during the atomization stage. Thus it was shown that the signal from silicon decreased 40 50 and 65% for times of 1,2 and 3 min after the addition of hydrofluoric acid. This loss of silicon is faster than that indicated by the mass loss curves which suggests that a fraction of the silicon is volatilized during the heating programme before the atomization stage. In summary the results basically agree with those reported previously for the analysis of glass7 indicating that the analytes are efficiently extracted from the solid matrix in a short time by the action of the hydrofluoric acid. The time is not critical as the integrated absorbance values are the same irrespective of whether the analyte is introduced into the furnace as a solution or as a slurry.The conve- nience of using hydrofluoric acid lies in its effective action as a chemical modifier which as originally defined by Ediger,20 is used to increase the volatility of the matrix. The practical consequence of the use of such a chemical modifier is a considerable increase in the lifetime of the tubes and platforms. 100 A 80 v) 60 .- 40 20 - 0) a ~ B 0 1 1 I 1 1 0 5 10 15 Time/min Fig. 1 Effect of hydrofluoric acid. (a) Fraction of solid mass remaining in the slurry and (b) ratio between the integrated absorbance of lead obtained from the supernatant and from the slurry. A B and C were obtained using 1 3 and 6% hydrofluoric acid respectively (see text for details) Optimization of the Furnace Programmes As Halls and co-workers showed,s-12 for a variety of analytical determinations the conventional drying and ashing steps can be replaced by a modified fast drying step thus permitting the analysis time to be shortened. Slavin et all3 have also shown that chemical modifiers can be omitted and rapid analyses can be obtained using both solutions and slurries.Such rapid slurry analysis has also been reported by Hinds et a1.I6 for soil and by Bendicho and de Loos-Vollebregt7 in their studies of glass materials.' Bearing this in mind the heating programmes were optim- ized. Determination of lead Platform atomization was used for the determination of lead. The suggestion from Hallss of a minimum ramp time (1 s) for the drying step was followed and the hold time and final temperature were studied.These parameters are related to a considerable number of factors including the volume of sample injected the mass of solids introduced into the furnace the physicochemical properties of the sample the performance of the instrument used and the temperature of the cooling water. When 1 O/o suspensions prepared in the presence of 3% hydrofluoric acid were used the drying temperature could be raised up to 400 "C and maintained for 15 s without any noticeable deterioration in repeatability or signs of sputtering. This agrees with the observations of Hinds et ~ 1 . ' ~ for soil suspensions in water. In fact it was confirmed that a 10 s hold time sufficed for the total drying of a 20 p1 aliquot.However as the electrothermal atomizer used switches automatically to the reduced or null gas flow condition 5 s before the beginning of the atomization step it was necessary to increase the drying time to ensure that the gas had completely removed the smoke before the atomization step. Thus a minimum of 15 s is necessary. The use of drying temperatures lower than 400 "C requires higher hold times and it was observed that the use of temperatures of 200 and 300 "C required hold times of 35 and 20 s respectively. When lop1 aliquots were used the hold times could be shortened to 25 15 and 12 s for drying temperatures of 200 300 and 400 "C respec- tively. Because of the low lead content in several of the DE samples studied the extreme situation of using 10 pl of 5Oh suspensions was also considered.Although this involves a mass of 500 pg of solid matter being introduced into the furnace a value which is above the recommended thresh- old,13 no noticeable deleterious effect on the repeat- ability was noted. This is because the mass of solid was in 0.20 A 0- 1200 1500 1800 2100 2400 Atomization ternperature/"C Fig. 2 Variation in the integrated absorbance with atomization temperature A 0.5 ng of lead; B 0.1 ng of copper; and C 0.14 ng of chromium in DE samples106 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 fact lower than thequoted value as a consequenceoftheeffect ofthe hydrofluoric acid. When using this high percentage the hold times quoted above had to be increased for 5 s to avoid smoke during the atomization step.The inclusion in the heating programme of a cool-down step prior to the atom- ization stage was also studied and no advantages were found. The results obtained when the atomization temperature was varied are summarized in Fig. 2. The integrated absorbance of lead decreased when atomization was per- formed above 1800 "C and a 1700 "C temperature was selected as adequate. The absorbance peak profile of lead obtained from DE suspensions is shown in Fig. 3. When the slurry was prepared in pure water the silica matrix produced a peak that was delayed and wider than that obtained using a similar suspension prepared in 3% hydrofluoric acid as indicated under Experimental. Under the recommended conditions the peak shape was nearly identical with that obtained from aqueous standards.Conventional heating programmes include a clean-up step to remove any residues from the tube. However the need for such a stage can also sometimes be questioned. If this step can be avoided total programme time is shortened and the lifetime of the tubes and platforms is increased. As DE samples are practically free of organic matter there is no risk of carbonaceous residues in the tube and so the omission of the clean-up step was studied. For this about 200 successive injections were performed using 1% DE suspensions prepared in a 3o/'a hydrofluoric acid medium using the recommended programme without a clean-up stage (Table 1) and the signal from lead was measured. No loss of sensitivity or repeatability was noted.Under this experimental condition the background signal slightly increased for the first runs remaining constant after 6-7 runs. Taking into account both the shortening of the heating programme time and the increase in the lifetime of the pyrolytic material the clean-up step was also omitted in the programme. However it must be noted that other metals which are more difficult to atomize than lead are retained in the atomizer and thus the tube and platform used for lead determination must not be used for the measurement of these metals. Determination of chromium and copper Wall atomization was used for the determination of both chromium and copper and the heating temperature pro- grammes were optimized in a similar way to that described for the determination of lead.The drying temperature had to be lower than that used for lead. Thus the maximum temperature was 200 "C with a hold time of 15 s for 20 pl of sample. Higher temperatures led to a loss of repeatability due to sputtering. 0 1 2 3 Timels Fig. 3 Absorption profile for Pb in DE samples. A Aqueous slurry amount of lead 0.46 ng integrated absorbance 0.158 s and B slurry prepared in the presence of 3% hydrofluoric acid amount of lead 0.36 ng integrated absorbance 0.123 s 0 1 2 3 4 5 6 Slurry concentration (%I Fig. 4 Effect of slurry concentration on integrated absorbance A chromium; B copper; and C lead. Bars indicate the standard deviation; n = 7 The results of experiments performed to study the influence of the atomization temperature for copper and chromium are summarized in Fig.2. For chromium it was necessary to use a temperature of 2600 "C. In the case of copper although a maximum and constant signal was obtained above 1800 "C a temperature of 2500 "C was selected as adequate for atomization. Using this tempera- ture the clean-up stage could be omitted without cross- contamination being observed when the tube was later used for the determination of other metals. The peak profiles of copper and chromium obtained from DE suspensions prepared in the presence of hydrofluoric acid were nearly identical with those obtained from aqueous standards. It is important to point out that the ageing of the tube significantly affected the integrated absorbance from the atomization of chromium. The analytical signal decreased when successive atomizations at 2600 "C were performed and the peak profile showed a tail which made it necessary to increase the atomization cycle up to 5 s after about 100 runs.Thus a periodical control of the deterioration of the pyrolytic tube is recommended when a high number of samples are to be analysed for chromium. A similar though less severe effect was noted for determinations of copper. Reproducibility and Calibration As has been discussed elsewhere,*' the percentage at which the suspensions are prepared is an important factor to be considered in the slurry methodology. For this a number of suspensions with different percentages of DE were prepared and the integrated absorbance values (seven measurements in each case) for the three analytes were obtained using the fast programmes studied. In all cases the percentages of the suspensions were chosen in such a way that the integrated absorbance values were in the linear response range of the instrument. As can be seen in Fig.4 the relative standard deviation (RSD) of the measurements was lower than -t 6% throughout the range studied; RSD values of k3.5 k3.0 and 2 2.7% were obtained for Pb Cr and Cu respectively in the middle points of the lines relating the analytical signal to the percentage slurry. Taking into account all the above observations calibra- tion using aqueous standards should be valid. To assess this several suspensions were prepared and standard additions calibration graphs obtained. The slopes of these graphs (Table 2) were nearly identical with those obtained from aqueous standards which validates the simplest calibration.Under the conditions studied characteristic mass values of 13 6 and 5 pg were found for Pb Cu and Cr respectively. The reliability of the approach was verified by analysing 14 commercial DE samples. The results (Table 3) revealed no significant differences (Wilcoxon T-test and useJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 107 ~~ Table 2 Slopes of the standard additions calibration graphs obtained for slurries prepared from DE samples and CRMs Slope* f SD/s ng-' Sample Lead Aqueous standard 0.328 1 f 0.0092 DE samples? 0.3232k0.0132 SARM$ 1 Granite 0.3332 f 0.0 153 BCS CRMS 375 Soda Feldspar 0.3295 f0.0173 NIST SRMj 688 Basalt Rock 0.3416 f 0.01 24 BCS CRM 376 Potash Feldspar BCS CRM 348 Ball Clay - - NIST SRM 1633a Coal Fly Ash 0.3295 k 0.01 13 h *The slopes were calculated from four-point standard additions.Eac were ureuared for each sample; SD indicates the standard deviation. Chromium Copper 0.9659 f 0.0961 0.7762f0.0112 0.9628 f 0.0303 0.9597 f 0.02 15 0.9702 f 0.03 15 0.7674 f 0.0223 0.7804 f 0.02 14 0.7795 k 0.01 92 0.9675 f 0.0257 0.7690f 0.0257 0.962 1 f 0.0201 0.7721 k 0.0206 0.96 1 1 f 0.0324 0.9689 f 0.0295 - 0.7745 k 0.0193 addition point was measured three times. Four different slurries ?Mean+ SD of the values obtained for 14 commercially available DE samples. $South Africa Bureau of Standards. $British Chemical Standard Certified Reference Material. YNational Institute of Standards and Technology Standard Reference Material.Table 3 Results for the determination of Pb Cr and Cu in DE samples and reference materials Element concentration*/pg g-I Sample DE- 1 DE-2 DE-3 DE-4 DE-5 DE-6 DE-7 DE-8 DE-9 DE- 10 DE-11 DE- 12 DE- 1 3 DE- 14 NIST SRM 1633a9 BCS CRM 3759 BCS CRM 3769 BCS CRM 3489 SARM 19 NIST SRM 6889 Lead Chromium Slurry Reference Slurry procedure value? procedure 1.9 k 0.2 3.1 f0.3 1.6 k 0.2 3.1 k 0.2 3.7 f 0.3 2.1 k 0.2 1.6 fO.1 2.7 k 0.2 3.8 f 0.3 2.4 k 0.2 2.7 f 0.3 3.9 ~t 0.3 2.0f0.1 3.5 k 0.2 7.8 f 0.7 71.3f3 - - 41.7 k 2.0 3.3 f 0.2 2.0 f 0.3 1.5 k 0.2 3.3 f 0.3 3.4 f 0.3 2.2 k 0.2 1.5k0.2 2.9 f 0.3 4.0 f 0.4 2.8 f 0.3 2.6 f 0.3 3.6 k 0.3 2.2 k 0.2 3.2 f 0.3 72.4 k 0.4 3.1 f 0.3 8 f 2 - - 40 3.3 k 0.2 7.8 k 0.5 7.1 k 0.5 13.2 k 0.7 12.6 f 0.7 7.4 f 0.4 13.2 f 0.6 14.4 k 0.8 10.7 f 0.7 11.6f0.7 8.9 f 0.5 7.1 f 0.4 13.1 f0.8 202 2 4 2.1 f 0.7 110k3 325 k 7 12.1 k0.8 8.6 f 0.5 23.1 2 2 12.8f0.6 *Mean f SD ( n = 7).?Obtained by acid-dissolution procedure (DE samples) or certified (CRMs). $No certified value. §For description of reference materials see Table 2. Reference value? 8.1 f 0.7 11.9f0.9 7.1 k 0.8 13.8 f 0.9 9.2 f 0.8 11.6f 1.0 7.8 f 0.5 14.8f 1.0 9.3 k 0.7 10.0 k 0.8 9.5 f 0.7 7.420.5 13.6f 1.0 196f6 2 5 f 2 t 4 109f 14 13.8 f 0.8 12 332f 19 Copper Slurry procedure 6.1 k 0.2 7.2 k 0.4 4.9 f 0.3 7.6 f 0.4 7.8 k 0.4 7.1 f 0.3 3.8 f 0.4 6.5k0.2 8.3 k0.4 6.9 k 0.3 6.7k0.3 7.3 f 0.3 4.8 k 0.1 2.8 A 0.3 4.9 f 0.2 12.4f0.5 89 k 2.0 7.1 00.3 123k2 - Reference value? 5.8 k0.5 7.4 k 0.6 5.1 f 0.4 8.2 A 0.5 8.1 k 0.4 7.3 f0.3 4.6 k 0.3 7.1 f 0.3 8.4 f 0.5 6.6 f 0.3 6.8 f 0.4 7.3 f 0.1 5.1 f0.2 7.5k0.6 118k3 3 k 1 5k1 - 12 (96N of regression lines) from those found using total dissolution of the samples in acid.As no DE samples with certified lead chromium and copper contents were available an addi- tional verification of the procedure was made by analysing several CRMs with similar silica contents (22-76%) to those of DE samples. The results which are also given in Table 3 confirm the reliability of the approach. Financial support from the Spanish Direcci6n General de Investigacih Cientifica y TCcnica (DGICYT) (Project 90-0302) is gratefully acknowledged. The authors also thank the Electron Microscopy Section of the University of Murcia for technical support. J. A. C. thanks the Venezuelan Foundation Gran Mariscal de Ayacucho for a scholarship. References Bendicho C.and de Loos-Vollebregt M. T. C. J. Anal. At. Spectrom. 1991 6 353. Stephen S. C. Littlejohn D. and Ottaway J. M. Analyst 1985 110 1147. Eames J. C. and Matousek J. P. Anal. Chem. 1980,52 1248. Langmyhr F. J. Stubergh J. R. Thomassen Y. Hanssen J. E. and DoleZal J. Anal. Chim. Acfa 1974 71 35. Siemer D. D. and Wei H. Anal. Chem. 1978 50 147. Nakamura T. Oka H. Morikawa H. and Sato J. Analyst 1992 117 131. Bendicho C. and de Loos-Vollebregt M. T. C. Spectrochim. Acta Parf B 1990 45 695. Halls D. J. Analyst 1984 109 1081. Halls D. J. and Fell G. S. Analyst 1985 110 243.108 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 10 Halls D. J. Mohl C. and Stoeppler M. Analyst 1987 112 185. 11 Halls D. J. Black M. M. Fell G. S. and Ottaway J. M. J. Anal. At. Spectrom. 1987 2 305. 12 Keating A. D. Keating J. L. Halls D. J. and Fell G. S. Analyst 1987 112 1381. 13 Slavin W. Manning D. C. and Carnrick G. R. Spectrochim. Acta Part B 1989 44 1237. 14 Bradshaw D. and Slavin W. Spectrochim. Acta Part B 1989 44 1245. 15 Bendicho C. and de Loos-Vollebregt M. T. C. Spectrochim. Acta Part B 1990 45 679. 16 Hinds M. W. Latimer K. E. and Jackson K. W. J. Anal. At. Spectrom. 1991 6 473. 17 Miiller-Vogt G. and Wendl W. Anal. Chem. 1981 53 651. 18 Miller-Ihli N. J. J. Anal. At. Spectrom. 1988 3 73. 19 Epstein M. S. Carnrick G. R. Slavin W. and Miller-Ihli N. J. Anal. Chem. 1989 61 1414. 20 Ediger R. D. At. Absorpt. Newsl. 1975 14 127. 21 Holcombe J. A. and Majidi V. J. Anal. At. Spectrom. 1989 4 423. Paper 2/03 78 1 E Received July 15 1992 Accepted October 8 1992

ISSN:0267-9477    

DOI:10.1039/JA9930800103

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 109 Effect of Surfactants in Flame Atomic Absorption Spectrometry With Pneumatic Nebulization Influence of Hydrophobic Chain Length Ana 1. Ruiz Antonio Canals and Vincente Hernandis Department of Analytical Chemistry University of Alicante 03071 Alicante Spain The behaviour of surfactants of different natures and chain lengths was studied in relation to the improvement in sensitivity that their use affords in flame atomic absorption spectrometry. The results show that when present the improvement in sensitivity is a consequence of a decrease in the aerosol mean drop size. For a given surfactant the decrease in drop size is caused by the decrease in surface tension in the solutions as the surfactant concentration increases.The shorter the surfactant chain length the greater is the efficiency of surface tension in diminishing the drop size to the point that the longest surfactants do not modify drop-size distribution at all and hence do not improve the sensitivity even though they exhibit the greatest capability to lower the surface tension of the solutions. Keywords Surfactant chain length; pneumatic nebulization; flame atomic absorption spectrometry; surface tension This paper is the continuation of a previous study' in which it was concluded that the addition of long-chain surfactants to sample solutions does not seem to offer a clear improvement in drop-size distribution (DSD) transport efficiency or analytical signal in flame atomic absorption spectrometry (FAAS) in spite of the sharp decrease observed in the surface tension values of the solutions. These results do not agree with those reported by other workers who claimed to have achieved significant signal improvements by adding surfactants.In a previous paper' it was pointed out that the length of the hydrophobic chain might play a relevant role in the effectiveness of the static surface tension and hence in DSD transport and signal. This hypothesis was based on the fact that the relaxation time for the surfactant molecules increases on increasing their chain length. The aim of this work was to evaluate the validity of this hypothesis. To this end the behaviour of surfactants of different natures and chain lengths was investigated in relation to the improvement in sensitivity they afford when used in FAAS and the causes of this improvement.Strictly some of these molecules cannot be considered as surfac- tants but were employed because of their chemical similar- ity to other longer molecules. Experimental All solutions contained potassium (5 pg ml-I) as analyte. Potassium was chosen because it does not precipitate with either hydroxyl ions or any of the other anions employed. Similarly all solutions contained a high concentration of NaNO (0.1 mol 1 - I ) to reduce ionization of potassium in the flame. It should be pointed out that some of the surfactants were employed as sodium salts whereas others were not. Thus all solutions contained a sodium concentra- tion high enough to act as an ionization buffer. Whenever the critical micelle concentration (CMC) was below 500 mmol 1- I the surfactant concentration was varied from zero to somewhere above the CMC.If the latter was above 500 mmol 1-I then this was the maximum concentration employed. All reagents employed were of analytical-reagent grade. The surfactants employed were decanoic acid (Fluka) sodium octanoate (Sigma) hexanoic acid (Aldrich) penta- noic acid (Merck) sodium decanesulfonate (Sigma) so- dium hexanesulfonate (Sigma) sodium dodecyl sulfate (SDS) (Fluka) hexadecyltrimethylammonium bromide (CTAB) (Fluka) and dodecyltrimethylammonium bromide (DTAB) (Sigma). Sodium salts of carboxylic acids were prepared by adding dilute NaOH solution to the acid just to a phenolphthalein colour change. All experiments were carried out with a concentric non- adjustable nebulizer (Meinhard Model TR-30-A3).The reason for using a non-adjustable nebulizer was to avoid the lack of repeatability usually associated with adjustable FAAS nebulizers in the relative positioning of gas and liquid outlets. The liquid flow Q was controlled by a peristaltic pump (Gilson Minipuls 2) and kept constant at 1.3 ml min-l throughout the experiments. The nebulizing air flow Qg was controlled by a previously calibrated precision flow meter (Cole-Parmer) and kept constant at 0.9 1 min-I. Drop-size distributions for the primary aerosol were measured with a laser Fraunhofer diffraction system (Mal- vern Instruments 2600C) fitted with a 63 mm length focal lens able to measure droplet diameters ranging from 1.2 to 118 pm. Version M5.4 software was used.Distributions were calculated by using a model-independent algorithm. Solvent transport efficiency was measured by an indirect continuous method.2 Wastes from the spray chamber were collected in a small beaker containing a small volume of water so as to act as a hydraulic closure. This beaker and that of the sample were placed on the plate of an automatic balance. After homogenization of the spray chamber the balance was set to zero and the loss of mass registered against time. The analytical signal (absorbance) was measured with an atomic absorption spectrometer (Perkin-Elmer 373) using a Meinhard nebulizer instead of the standard adjustable nebulizer. The experimental conditions are given in Table 1. Table 1 FAAS operating conditions Wavelengthhm Slit-widthlnm Lamp current/mA Height above burner/mm Acetylene flow ratell min-I Air flow rate (total)/l min-' Air flow rate (nebulizer)/l min-' Liquid flow ratelm1 min-' Integration timels 766.5 2.0 12.0 8.0 1.3 8.4 0.9 1.3 5.0110 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL.8 Table 2 Physical properties of surfactant solutions Surfactant C,HI,C02Na CSH ,C02Na C4H9C02Na C4HgC02H IOH21 S03Na C6H ,S03Na *o=Surface tension. t q = Viscosity. &I= Density. Concentration/ mmol 1 - I 0 26.0 65.0 130.0 195.0 0 60.0 150.0 300.0 400.0 0 125.0 250.0 375.0 500.0 0 125.0 250.0 375.0 500.0 0 7.0 18.0 29.7 63.0 0 24.0 54.0 120.0 225.0 0 8.0 16.0 24.0 66.0 0 125.0 250.0 375.0 500.0 0 0.5 1 .o 2.0 4.0 0 0.2 0.4 0.8 2.0 0 1 .o 2.0 3.0 15.0 dc( x 103y N m-I 72.0 52.1 41.7 38.3 37.6 72.4 50.4 36.2 23.4 31.5 72.0 61.8 53.6 50.5 46.4 72.0 70.4 68.3 66.4 64.3 72.5 61.9 51.9 41.8 37.2 72.0 59.6 51.3 41.7 34.2 73.2 50.4 43.3 39.4 38.3 72.2 61.9 56.2 51.5 47.8 72.3 53.2 42.0 37.6 35.4 72.4 62.7 49.0 37.5 33.1 72.4 48.8 42.9 39.1 36.6 qt( x 103y ps( x I 0-3y N s m-2 kg mq3 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1.1 1 .oo 1.1 1.01 1 .o 1 .oo 1 .o 1.01 1.1 1.01 1.2 1.01 1.3 1.01 1 .o 1 .oo 1.1 1 .oo 1.2 1.01 1.3 1.01 1.4 1.01 1 .o 1 .oo 1.1 1 .oo 1.1 1.01 1.2 1.01 1.3 1.02 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1.1 1 .oo 1.1 1 .oo 1.1 1.01 1 .o 1 .oo 1.1 1 .oo 1.1 1.01 1.2 1.02 1.3 1.02 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo 1 .o 1 .oo The absorbance measurements were always made against blanks containing the same surfactant and NaNO con- centration as the sample solution but free from potas- sium.Surface tension was measured by the drop-weight method and viscosity was determined with an Ostwald viscometer. The experimental procedure was as follows. For each surfactant solution the physical parameters DSD tran- sport efficiency and analytical signal were measured con- secutively in the same work session. Because of this some discrepancies in DSD transport efficiency or signal could arise between similar solutions as these values were usually obtained many days apart.In order to account for this relative values were used to compare the behaviours of the different surfactants. For each of the magnitudes studied these relative values were obtained by dividing the values of all the solutions making up a series by the value corresponding to the surfactant-free solution. This solution is referred to in the text by a subscript zero. Although SDS sodium decanesulfonate and sodium hexanesulfonate do not strictly belong to the same homo- logous series the results have been grouped for sim- plicity.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 1.4 - A 1.2 - 1.0 - C + ! s = l = l 1 1 1 ( d ) I I 1.4 1.2 1 .o d.5 Fig. 1 Relative variation of V3.0 versus surface tension. (a) A Sodium pentanoate; B sodium hexanoate; C sodium octanoate; and D sodium decanoate.(b) A Pentanoic acid; and B hexanoic acid. (c) A Sodium hexanesulfonate; B sodium decanesulfonate; and C SDS. (d) A DTAB; and B CTAB Results and Discussion Physical Properties of the Solutions Table 2 gives the physical properties of each of the solutions employed. From these results it appears that viscosity and density change very little from one solution to another. The only significant increases corresponded to the more concen- trated solutions of short-chain surfactants such as sodium pentanoate sodium hexanoate sodium octanoate and sodium hexanesulfonate. However the surface tension significantly decreased with increasing concentration for all the surfactants employed although this decrease was more pronounced for those with long hydrophobic chains.The fact that within a homologous series short-chain surfactants need a high concentration to achieve a substantial decrease in surface tension causes the CMC not to be reached in some instances as solution concentrations were limited to 500 mmol 1-* in order not to clog the nebulizer. This was the case for sodium pentanoate sodium hexanoate and sodium hexanesulfonate. On comparing the surface tension values of pentanoic and hexanoic acids with the corresponding values for their 1.4 1.2 1 .o 1.4 1.2 1 .o I I I 40 60 80 I 40 60 80 0/103 N m-' Fig. 2 Relative variation of solvent transport rate E versus surface tension. (a) A Sodium pentanoate; B sodium hexanoate; C sodium octanoate; and D sodium decanoate. (6) A Pentanoic acid; and B hexanoic acid.(c) A Sodium hexanesulfonate; B sodium decanesulfonate; and C SDS. (4 A DTAB; and B CTAB112 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 sodium salts carboxylic acids are seen to lower the surface tension more quickly than their salts. It was not possible to study the behaviour of acids longer than C6 owing to their lack of solubility. Drop Size Distribution of the Primary Aerosol Aerosol characterization was done by means of the volume percentage contained in droplets smaller than 3.0 pm in diameter (V3.0) as this magnitude represents a coarse estimate of the fraction of primary aerosol that would eventually reach the flame. Fig. 1 shows the relative variations of V3.0 with solution surface tension. From these results it appears that for long- chain surfactants such as CTAB SDS and DTAB there are no significant variations in DSD with increasing surfactant concentration in spite of the fact that surface tension values show a sharp decrease; for the other surfactants V3.0 increases ( i e .the droplets become smaller) with decreasing surface tension as the surfactant concentration is increased; and in most instances it appears that on comparing solutions with similar surface tension values the shorter chain surfactant provides a finer distribution than its longer chain homologue although sodium hexanoate clearly does not follow this trend. Transport The relative variations in solvent transport rate versus surface tension are shown in Fig. 2. In spite of the inherent lack of precision associated with these measurements some conclusions can be drawn as follows.Short-chain sodium salts show transport enhancements lower than the corresponding V3.0 enhancements. This behaviour can be ascribed to the decrease in volatility caused by the increasing surfactant concentration. This decrease in volatility should make the amount of solvent transported to the flame in vapour form decrease; this would in turn fully or partially compensate for the increase in the amount of solvent transported in liquid form this increase being caused by the reduction in the mean size of 1.8 1.6 ' 1.4 1.2 1 .o TI* the DSD. Hence as the analyte is transported only in the liquid fraction the increase in surfactant concentration in these instances should be associated with an analyte transport increase greater than the solvent transport increase.There is no solvent transport enhancement for long-chain surfactants (SDS CTAB and DTAB) in spite of the low surface tension values achieved. These results are in agreement with the distribution data which likewise showed no variation. In addition for long-chain surfactant series the variations in concentration are much smaller; as a result substantial volatility variations are not likely. Hence one should not expect significant variations in analyte transport in these instances. Agreement also exists for carboxylic acids between the DSD and solvent transport. This indicates that volatility does not seem to be markedly influenced by the increase in surfactant concentration. Two reasons may account for this in these series the surfactant concentration does not reach values as high as with the short-chain sodium salts; and these compounds are not ionic but molecular and hence their influence on water volatility should be much smaller.Analyte transport should therefore follow the same trend as solvent transport. B A 1.2 1-4- 1 .o 40 60 80 Signal The relative variations in absorbance versus surface tension are shown in Fig. 3. It can be seen that a signal increase results in all instances (except with CTAB) as the surface tension decreases this increase also being of little signifi- cance for SDS. The SDS and CTAB both long-chain surfactants are the most effective among the surfactants employed in diminishing the surface tension of the solu- tions.This behaviour is in good agreemnt with the fact that the DSD and transport rate hardly vary with increasing surfactant concentration. Obviously the absorbance values obtained in this way are far removed from those which would be obtained with an organic solvent with similar viscosity and surface tension values3 Within any given homologous series it basically holds that on comparing A A 40 60 80 Fig. 3 Relative variation of analytical signal A versus surface tension. (a) A Sodium pentanoate; B sodium hexanoate; C sodium octanoate; and D sodium decanoate. (b) A Pentanoic acid; and B hexanoic acid. (c) A Sodium hexanesulfonate; B sodium decanesulfonate; and C SDS. (6) A DTAB; and B CTABJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. FEBRUARY 1993 VOL. 8 113 solutions with similar surface tension values the relative absorbance increase is greater for the surfactant with the shorter chain length.Relative absorbance enhancements are always greater than solvent transport increases. In some instances the absorbance increases markedly even though the transport hardly varies. Clearly the explanation given under Transport would also apply here. Hence absorbance enhancements are closer to V3.0 enhancements than to solvent transport increases. Conclusions Overall the results seem to show that with aqueous surfactant solutions surface tension does not have the dominant role that it plays with pure solvents or solvent mixtures. The surface tension values achieved with long- chain surfactants are inefficient in decreasing the mean size of the DSD or in increasing transport efficiency. The fact that surface tension becomes more ‘effective’ with decreas- ing chain length can be explained by taking into account that the static rather than dynamic surface tension values were employed and these values may not be applicable to nebulization processes that take place in less than 1 ms.In other words surfactant molecules take time to re-establish surface tension equilibrium which is broken when a new surface is generated. If the nebulization process is much faster than surface re-equilibration then the surfactant solution would be expected to behave as it if contained no surfactant at all its actual surface tension being that of the pure solvent (hydrodynamic effect4). In addition it is known that the time required for aqueous solutions of aliphatic alcohols to reach surface equilibrium increases with increasing chain length and decreasing c~ncentration.~ The results obtained here seem to support this explana- tion.Thus on comparing solutions with similar surface tension values within a homologous series the molecules with a shorter chain length appear to cause a greater drop- size reduction and also greater increases in transport and signal. Nevertheless the transport enhancements due to drop- size reduction do not seem to be large enough to account alone for the signal enhancements obtained. Hence other contributing factors probably exist. A possible additional cause could be an improvement in atomization efficiency. This would be supported by the fact that when the mean drop size of the primary aerosol decreases the amount of tertiary aerosol ( i e . the aerosol just entering the atomiza- tion cell) not only increases but also becomes fineI.6 ( i e . transport enhancement is mainly contributed to in the very small diameter distribution range) thus improving the atomization efficiency in the flame. The Comision Interministerial de Ciencia y Tecnologia (CICYT) (Spain) is acknowledged for financial support (grant No. PB88-0288). References 1 2 3 4 5 6 Mora J. Canals A. and Hernandis V. J. Anal At. Spectrom. 1991 6 139. Maessen F. J. M. J. Seeverens P. J. H. and Kreuning G. Spectrochim. Acta Part B 1984 39 1 17 1. Mora J. Hernandis V. and Canals A. J. Anal. At. Spectrom. 1991 6 573. Mans C. Llorens J. and Costa J. Invest. Cienc. 1988 136 78. Addison C. C. J. Chem. Soc. 1945 98. Canals A. Hernandis V. and Browner R. F. Spectrochim. Acta Part B 1990 45 591. Paper 2/035 I5 D Received July 3 1992 Accepted September 9 I992

ISSN:0267-9477    

DOI:10.1039/JA9930800109

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 115 Sensitive ‘One Drop’ Flame Atomic Absorptiometric Determination of Cadmium in Botanical Samples Using Direct Nebulization of Chloroform Extract lsao Kojima and Shinji Kondo Laboratory of Analytical Chemistry Department of Applied Chemistry Nagoya Institute of Technology Gokiso-cho Sho wa-ku Nagoya 466 Japan After microwave digestion of solid samples with an acid mixture in a pressurized double poly(tetrafluoroethy- lene) bom b and the removal of iron in the sample solution by extraction with 2-hydroxy-4-isopropylcycloheptatri- enone dissolved in benzene the cadmium-ammonium pyrrolidin-I-yldithioformate (APDC) complex was extracted into chloroform. Direct nebulization of the chloroform extract of cadmium-APDC complex into the flame gave a very sensitive signal intensity.The background corrected signal intensity obtained by nebulizing 40 pI of the extract was about 4.5 times larger than that obtained by nebulizing 100 pI of aqueous solution and the detection limit obtained with an injection volume of 40pl was 1.2 ng ml-1 or 50 pg [signal-to-noise ratio (S/N)=3]. Cadmium was determined by ‘one-drop’ flame AAS with deuterium background correction with an injection volume of 40 pl of chloroform extract. The present method was successfully applied to the determination of cadmium in botanical certified reference materials National Institute for Environmental Studies certified reference material (NIES CRM) No. 1 Pepperbush and No. 10 Rice Flours (low and medium) and National Institute of Standards and Technology Standard Reference Materials (NIST SRMs) 1571 Orchard Leaves 1572 Citrus Leaves and 1575 Pine Needles and the results (1 12 -t 6 and 29 f 2 ng g-I) for Orchard Leaves and Citrus Leaves were in good agreement with the certified values (1 10 f 10 and 30 -t 10 ng g-l).Keywords Extraction of cadmium-ammonium pyrrolidin-I-yldithioformate complex; flame atomic absorption spectrometry with discrete nebulization; botanical standard samples; microwave acid digestion; cadmium Trace element analysis has become important from toxico- logical and nutritional points of view. It is well-known that cadmium is a toxic element of particular importance in Japan. For example the disease Itai-Itai was caused by consumption of rice contaminated with cadmium which is a staple food for Japanese.Therefore to know accurately the concentration of cadmium in rice is very important. Chelate extraction is a very useful method for trace metal preconcentration prior to atomic absorption sepctrometry (AAS).’ The common organic solvents suitable for metal extraction e g . carbon tetrachloride and chloroform make it easier to concentrate the trace levels of metals in the sample solution into a small volume of organic extract because of their lower solubility in water. On the other hand organic solvents e g . 4-methylpentan-2-one [ isobutyl methyl ketone (IBMK)] which are frequently used in flame AAS make difficult the complete recovery of the solvent for extraction with high ratios of aqueous to organic solvent because of its higher solubility in water.‘One-drop’ flame AAS is a rapid and very convenient method for determining trace levels of metals in very limited volumes of sample solutions especially in the organic extracts after concentration of metal chelates by extraction. A detailed study on the combined use of extraction of trace levels of metals and ‘one-drop’ flame atomic absorptiometric determination of metals in some biological samples has been r e p ~ r t e d . ~ * ~ The aim of this study was the construction of a combined technique for the preconcentration of trace amounts of cadmium and the determination by sensitive ‘one drop’ flame AAS and application of the method to the determina- tion of cadmium in some botanical standards. Experimental Apparatus An atomic absorption spectrometer equipped with a 100 mm burner head and a deuterium background corrector Seiko Model SAS-727 was used for measurement with a fuel-lean air-acetylene flame under the optimum operating conditions wavelength 228.8 nm; observation height 13.5 mm above burner head; air flow rate 17 1 rnin-l (250 kPa); acetylene flow rate 3.25 1 min-l (98 kPa); lamp current 10 mA; sample flow rate 4.0 ml min-l; and deuterium lamp on.Less than 100 p1 of the sample solution were injected with a micropipette (Gilson P-200) into the poly(tetrafluoroethy1ene) (PTFE) funnel coupled directly to the nebulizer needle. The signal intensity was recorded on a strip-chart recorder (National VP-66 12 A). Sample decom- position was carried out in a closed double PTFE vessel with a polypropylene jacket (P-25 from San-ai Kagaku) by microwave heating.4 An unmodified Mitsubishi RO 2500 domestic microwave oven (Mitsubishi RO 2500) was used at intermittent heating corresponding to 200 W (14 s on and 20 s off) for the digestion of samples in a PTFE bomb.A PTFE vial of 7 ml capacity was thoroughly rinsed first with 3 mol 1-1 hydrochloric and then with 2 mol 1-l nitric acid and finally with de-ionized water. Reagents Metal stock solutions 2 mg g-’ in 0.5 mol 1-1 nitric or hydrochloric acid were prepared by dissolving metals (Cd Cu Fe Zn of 99.999% purity from Mitsuwa Chemicals) and MnOt (Specpure grade from Johnson Matthey) in nitric or hydrochloric acid and diluting with water by mass. Aqueous ammonium pyrrolidin-1-yldithioformate (APDC) solution ( 1 O/o) was prepared by dissolving APDC (Nacalai Tesque) in water immediately before use.Working standard aqueous metal solutions in 0.1 mol 1-1 hydrochloric acid were prepared by diluting the metal stock solution with water and hydrochloric acid to appropriate metal con- centrations. Working standard chloroform solutions containing the cadmium-APDC complex were prepared by extracting the mixed solution containing 5 ml of cadmium standard solution and 5 ml of 1% APDC solution with 0.5 ml of chloroform. Chloroform of guaranteed-reagent grade was used without further purification. 2-Hydroxy-4-isopro- pylcycloheptatrienone (HIPT) (Takasago Perfumary) was116 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 dissolved in benzene as received.The acids used were of super special grade (Wako). Milli-Q (Millipore) deionized water of 18.1 M a cm-* specific resistivity was used throughout. Sample Decomposition A sample of less than 0.5 g dry mass is placed in a Teflon perfluoroalkoxy (PFA) Tuf-Tainer vial (inner vessel of 7 ml capacity Pierce Chemical) with an appropriate volume (2.5-3.5 ml) of an acid mixture of nitric perchloric hydrochloric and hydrofluoric acids (20 + 3 i- 1 + 1). After capping the inner vial by hand the vial is placed in the outer PTFE vessel (25 ml capacity) containing 2.0 ml of 2 mol 1-' sodium hydroxide solution. The outer vessel is tightly closed in a polypropylene jacket by fastening with a wrench. Six bombs including one blank are located symmetrically on the carousel of a microwave oven and simultaneously heated for 5 min with 100 ml of water in a 100 ml beaker placed at the centre of the carousel (to keep the magnetron from damage) at an intermittent power (200 W) and then heated again for another 4 min at the same power after removal of the beaker of water from the oven.The inner vial is taken out of the bomb after cooling at room temperature (about 25 "C). The digest in the vial is completely evaporated to dryness in a specially designed PTFE drying chamber on a hot-plate and under an infrared lamp.5 The dried residue is dissolved in 1.5-5.0 ml of 0.2 moll-' perchloric acid in the same vial and the total mass is weighed. The final sample solution thus obtained is used for the removal of iron and separation of cadmium by extraction.Extraction Procedure After the complete removal of iron(u1) in the sample solution by extracting with 3 ml of 0.01 mol 1-' HIPT in b e n ~ e n e ~ ? ~ washing the aqueous phase with 1 ml of benzene and removing the benzene completely by blowing air onto the surface of the aqueous phase the volume of aqueous solution remaining is placed in a glass test-tube with a stopper and weighed. Into this test-tube 1.5-5.0 ml of 1% APDC solution and 0.15-0.50 ml of chloroform are placed. After shaking for 2 min by hand the test-tube is left to stand until complete phase separation is obtained and 30 or 40 pl of the chloroform extract is directly injected into the flame for AAS measurement of cadmium as in previous work.*v3 The signal height on the strip-chart recorder is read and the metal content in the chloroform extract found by consulting the calibration graph.Results and Discussion Effect of Injection Volume The direct nebulization of the chloroform extract of the cadmium-APDC complex showed spike-like and/or very smooth signal profiles very similar to those obtained by nebulizing an aqueous cadmium solution corresponding to discrete and continuous nebulization.' The smooth signal profile obtained with a large injection volume is different from the interesting signals obtained by nebulizing the same injection volume of chloroform extracts of copper cobalt and nickel c o m p l e ~ e s . ~ ~ ~ The discrete nebulization of a small volume of the chloroform extract gave a spike-like signal. The background corrected signal height increases with an increase in the injection volume up to a volume of about 80 pl with a constant cadmium concentration and then remains constant as is evident from Fig.1. The constant signal height is the same as that obtained by continuous nebulization of the chloroform extract. On the other hand the background signal height increases with an increase in the injection volume only at injection volumes larger than 60 pl as is evident from Fig. 1. Therefore deuterium background correction for chloroform alone is unnecessary for an injection volume of less than 50 pl. However the nebulization of a chloroform extract contain- ing a high concentration of APDC gave a constant and low signal height even with an injection volume of less than 50 pl depending on the concentration of APDC in the chloroform extract.Therefore deuterium background cor- rection should be used for practical analysis. As a typical example background corrected signal profiles and back- ground signals obtained by injecting 40 pl of chloroform extract and chloroform alone are shown in Fig. 2. It can be seen that the background signal caused by chloroform alone did not appear and that the background signals from the chloroform extract did appear. However the signals after deuterium correction did not appear in spite of the background signal caused from APDC in the chloroform extract. The signal height obtained for a chloroform extract containing 0.1 5 pg of cadmium per millilitre of chloroform was constant after deuterium correction. The relative standard deviation (RSD) obtained in this case was 0.8%.The RSD obtained even with 20 pl was 1.7%. Effect of Some Factors on Signal Height Effects of burner height sample flow rate and acetylene flow rate on signal height were studied with a constant injection volume of 40 pl of chloroform extract contain- ing 0.15 pg of cadmium per millilitre of chloroform. With increasing burner height the signal height and the back- ground signal height decreased. However the background corrected signal height was almost constant and the small background signal height caused from APDC in chloro- form was observed at an observation height higher than 12 mm. The background corrected signal height obtained at different sample flow rates showed an almost constant signal height but the background signal was observed only at a high sample flow rate.The background corrected signal height obtained at different acetylene flow rates was almost constant but the background signal increased gradually at an acetylene flow rate of less than 2.75 1 mine' and more than 4.0 1 min-' and also a large injection volume gives rise to easy flame lift-off and extinguishing of flame at low acetylene flow rate. From these results the optimum operating conditions were selected as described under Experimental. 100 E E 2 0 a E - 50 C 0 .- i?j 0 1 I 1 50 100 " 150 Injection volume/pI Fig. 1 Effect of injection volume on background corrected signal heights and background signal heights A background corrected signal height of 0.15 pg ml-I of Cd; B background signal height from chloroform alone; and C background signal height from chloroform extractJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL.8 117 B B C I I -I m i n d I Time - Fig. 2 (a) Background corrected signal heights and (b) background signal heights A chloroform alone; B 0.15 pg of Cd per ml of chloroform; and C chloroform extract Calibration Graph With an increase in the injection volume the slope of the linear calibration graph increased up to about 80 p1 of the injection volume as is expected from Fig. 1. Considering the RSD of the signal height the background signal intensity and the volume of the chloroform extract an injection volume of 20-40 pl was used for the determina- tion of cadmium by the proposed method. As an example the background corrected calibration graph and back- ground signal height obtained by injecting 40 pl of chloro- form extract are shown in Fig.3 with the calibration graph obtained by injecting I00 pl of aqueous cadmium solution. From the slopes of calibration graphs obtained with the extract and aqueous solution under their optimum operat- ing conditions the sensitivity obtained with the extract was 4.5 times higher than that obtained with the aqueous solution. The repeatability was very good 0.8% for an injection volume of 40 pl. The detection limits obtained with injection volumes of 20 and 40 pl were 2.6 and 1.2 ng ml-I (S/N=3) of cadmium in the chloroform extract respectively. 0 0.1 0.2 0.3 0.4 Cadmium/pg ml-’ of CHCI Fig. 3 Calibration graphs and background signal height with OS0h APDC (aqueous solution) 500 p1 of chloroform and Voa Vaq = 1 :20 for A chloroform extract; B aqueous solution; and C background signal height for chloroform extract Extraction of Cadmium-APDC Complex increasing pH at pH values higher than 0.7 and also HIPT in benzene at a pH of less than 1.5.Of the many organic extracting agents for metals APDC is one of the most suitable reagents for use with highly acidic solutions. Effect of Foreign Metal Ions Metal extraction behaviour with APDC was tested and the Judging from the metal contents in standard samples used results are shown in Fig. 4. The cadmium- in the present study the effects of iron zinc and manganese APDC complex was easily extracted into chloroform from were studied. In the presence of 20 pg of iron 35 pg of zinc 0.5% APDC solution at pH higher than 0.6.On the other and 200 pg of manganese the recovery of 1.5 pg of hand the percentage extraction of zinc increases with cadmium was tested. The results were very satisfactory i.e.,118 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 ~~ ~ Table 1 Results for cadmium in botanical standards Standard Sample Final mass/ volume/ mg ml NIES CRM No. I NIES CRM No. 10 NIES CRM No. 10 NIST SRM 1571 NIST SRM 1572 NIST SRM 1575 Pepperbush 100 5.0 Rice Flour (low) 500 1.5 Rice Flour (medium) 400 4.0 Orchard Leaves 200 2.0 Citrus Leaves 300 1.5 Pine Needles 200 2.0 *Not certified. CHClJ Pl 500 150 400 200 150 200 Injection volume/ Pl 40 30 40 40 40 40 Observed value/ ng g-' 6920 k 100 26+ I 308k11 112k6 2 9 k 2 201 k 7 Reference value/ ng g-' n 6700+500 6 23+3 5 320+20 4 11Ok10 3 30k10 3 220+60* 5 C (I 0 0.5 1 .o 1.5 PH Fig 4 Effect of pH on extraction of metals with 0.5% APDC (aqueous solution) 500 pl of chloroform and Vo, Vaq= 1:20 for A Cu Co and Ni; B Cd; C Zn; and D Mn 99% recovery even at an aqueous solution to chloroform volume ratio of 20:1 as expected from separation of cadmium from iron manganese and zinc by extraction. The effect of other metal ions was not tested because of their low content and their simultaneous extraction with cad- mium.Determination of Cadmium in Standard Botanical Samples With the proposed method cadmium was determined in National Institute for Environmental Studies (NIES) certi- fied reference materials (NIES CRMs) No.1 Pepperbush and No. 10 Rice Flour (low and medium) and National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) 1 5 7 1 Orchard Leaves 1 5 72 Citrus Leaves and 1575 Pine Needles. The results obtained are shown in Table 1. The cadmium content in the samples was easily calculated from the sample mass used the final sample solution obtained after decomposition the sample solution used for extraction the copper content found in the chloroform extract and the precise volume of chloro- form used for extraction. The precise volume of chloroform used for extraction was calculated from the mass and density. The results obtained by the proposed method were in good agreement with each other and also with the certified or reference values. The authors express their sincere thanks to Professor H. Wada for her deep interest in this work. References 1 Cresser M. S. Solvent Extraction in Flame Spectroscopic Analysis Butterworth London 1978. 2 Kojima I. Nakashima N. Isoyama H. Uchida T. and Iida C. J. Anal. At. Spectrom. 1988 3 583. 3 Kojima I. Fukumori H. and Iida C. Anal. Sci. 1992,8 533. 4 Kojima I. Kato A. and Iida C. Anal. Chim. Acta 1992,264 101. 5 Isoyama H. Uchida T. Oguchi K. Iida C. and Nakagawa G. Anal. Sci. 1990 6 385. 6 Dyrssen D. Trans. R. Inst. Technol. Stockholm 1962 No. 7 Uchida T. Kojima I. and Iida C. Anal. Chim. Acta 1980 116 205. 188 pp. 1-50. Paper 2/03255D Received June 22 1992 Accepted October 13 1992

ISSN:0267-9477    

DOI:10.1039/JA9930800115

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 119 Determination of Butyltin Compounds in River Sediment Samples by Gas Chromatography- Atomic Absorption Spectrometry Following ln Situ Derivatization With Sodium Tetraethylborate Yong Cai Spyridon Rapsomanikis* and Meinrat 0. Andreae Biogeochemistry Department Max Planck Institute for Chemistry P. 0. Box 3060 Saarstraase 23 W-6500 Mainz Germany A method for the determination of butyltin compounds in river sediments is described. The method involves in situ ethylation of organotins by sodium tetraethylborate in aqueous buffered solution simultaneous purging and trapping of ethylation derivatives and detection by atomic absorption spectrometry. The absolute detection limits (30 of baseline noise) for mono- di- and tributyltin are 0.08 0.34 and 0.11 ng of tin respectively.The concentration detection limits achieved are 9,38 and 12 ng of tin per gram of sediment (dry mass) respectively. The technique has been successfully applied to the determination of tributyltin and dibutyltin in a spiked river sediment. For the accurate measurement of butyltin compounds in river sediment a method based on extracting sediment with various volumes of solvent is used. Keywords Butyltin compounds; ethylation derivatization; sediment; gas chromatography-atomic absorption spectrometry; en vironmen tal analysis Tin is unsurpassed by any other metal in the number of applications of its organometallic compounds. These in- clude use in poly(viny1 chloride) stabilizers industrial catalysts industrial and agricultural biocides and wood- preserving and antifouling agents.World consumption of organotins in 1986 was 35 x lo6 kg.' The continuously growing interest concerning the biogeo- chemical cycle of organotins is due not only to the use of large amounts of organotin compounds but also to their impact on the environment. Elemental and inorganic forms of tin appear to have negligible toxicological effects in humans or wildlife. In contrast organotin compounds especially tributyltin (TBT) exhibit elevated fat solubility and consequently an enhanced ability to penetrate biologi- cal membranes thereby posing a greater toxic and environ- mental risk.2 The toxicity of organotin compounds to aquatic organisms is thought to increase with an increase in the number of butyl substituents from one to three and then to decrease with the addition of a fourth butyl group.' Tributyltin is by far the most toxic to aquatic organisms of all organotin compounds and may be the most acutely toxic chemical to aquatic organisms that is deliberately introduced into water.' For this reason the use of TBT- containing antifouling paints is now controlled or banned in several countries.However the TBT controversy is not over. The use of TBT paints on many large vessels continuess and the illegal use of TBT on small craft is still widespread. This compound can also enter the aquatic environment via wastewater as TBT is used as a biocide for the preservation of wood textiles paper and stonework. It is also used as an agricultural disinfectant and as a stabilizer in plastics.6 To date methodologies for the assessment of the environmental risk of TBT have not been uniformly a p ~ l i e d .~ To understand better the environmental behav- iour of butyltins during for instance multi-media tran- sport degradation and metabolism it is necessary to analyse for trace amounts of TBT and its degradation products dibutyltin (DBT) and monobutyltin (MBT) in various environmental matrices. Techniques for determining butyltin compounds in en- vironmental water samples are well but the techniques for the determination of butyltin in tissue and sediment are less well devel~ped.'~J~ Stephenson et a1.I6 *To whom correspondence should be addressed. found that laboratories agreed only within a factor of 2-3 in determinations of butyltins in mussel tissue and sediments during an intercomparison exercise between seven labora- tories.Various techniques for the measurement of TBT in sediments have been reported. Many of these methods employ derivatization and separation by standard chroma- tographic techniques and subsequent determination by atomic absorption spectrometry (AAS),17J8 mass spectro- metry,''J9 flame p h o t ~ m e t r y ~ ~ ? ~ ~ ~ ~ ~ and atomic emission spe~trometry.~~J~ Two methods in particular have been used for the derivatization of the relatively involatile organotin com- pounds bound to chlorides oxides hydroxides or unknown counter ions hydride g e n e r a t i ~ n ' ~ J ~ J ~ J ~ and alkylation with Grignard r e a g e n t ~ . ~ ~ J ~ - ~ ~ Both of these methods have disadvantages when applied to environmental samples.The hydride generation method using sodium tetrahydroborate (NaBH,) is convenient for the derivatization of oganotin compounds but the signal has been found to be suppressed in the presence of diesel oil and sulfides both of which may occur at high levels in sediment ~ a m p l e s . ~ ~ * ~ ~ Alkylation with Grignard reagents can only be performed on com- pletely dry media hence organometallic species in aqueous samples including water and sediment have to be ex- tracted into an organic phase that must be dried prior to the alkylation. The large number of handling steps required affects the accuracy and precision of the determination. Therefore the development of a new organotin derivatiza- tion technique is desirable.The use of sodium tetraethylborate (NaBEt,) as a deriva- tization reagent was initiated for the determination of methyllead and methylmercury ionic corn pound^.^^^^* It acts as an aqueous-phase ethylating reagent quantitatively transferring Et- ions to methyllead methylmercury and inorganic lead and mercury ions. The Sn-C2H bond once formed is more thermally stable than the Sn-H bond. Recently NaBEt has also been used as an ethylation reagent for the determination of organotins in sediments by Ashby and Craig.29v30 However their procedure necessitates a number of handling steps derivatization in ethanol and injection of a definite aliquot into the gas chromato- graph y-atomic absorption spectrometry (GC-AAS) system. In this paper the application of the ethylation technique for the determination of butyltin compounds in environ- mental sediments is reported.The method involves in situ ethylation of butyltin species in aqueous solution,120 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 solution cryogenic trapping and separation and subsequent detection by AAS. The technique has proved reliable accurate and convenient for determining TBT in river sediments. Experimental Apparatus Analysis was performed employing a slightly modified ver~ionl~v~~ of the hydride generation GC-AAS technique (no water trap was used). It involves derivatization of butyltin compounds in sediment extract to the correspond- ing butylethyltin derivatives by reaction with NaBEt,. The volatile species are purged from the solution into a cold trap filled with chromatographic packing.They are subsequently separated by controlled heating of the trap and detected by AAS with an electrothermally heated quartz furnace. A round-bottomed glass cylinder (approximately 60 ml) with an injection port containing a Teflon-coated silicone-rubber septum is used as a reaction vessel and is connected to a cold trap via a four-way valve. The cold trap total length 90 cm is constructed from 6.0 mm 0.d. x 4 mm 0.d. x 4 mm i.d. borosilicate glass. Prior to packing the empty column and the glass reaction vessel are silanized to deactivate the internal surfaces. An Ahlborn Model T683-2 NiCr-Ni thermocouple was fitted on the surface of the column and was then wrapped with a 4.7 m longx0.5 mm thick Nichrome wire (5.5 Q m-l).The butylethyltin derivatives were trapped on a packing of 4.0 g of 3% SP 2100 on Chromosorb G AW DMCS (60-80 mesh) (Supelco). The cold trap was heated with a variable transformer coupled to a temperature controller which limited the maximum temperature to 190-200 "C. Connections were made with Teflon Swagelok unions and Teflon tubing (3.2 mm 0.d.). The unions and tubing were surrounded with a 1.5 m heating string (Heraeus 236 W maximum). The tempera- ture of the connections was maintained at 120 "C by a variable transformer. Tin compounds were detected with a Perkin-Elmer Model 3030B atomic absorption spectrometer equipped with an electrodeless discharge lamp. The quartz furnace constructed in house (83 x 7.7 mm i.d.) was wrapped with a double strand of Nichrome resistance wire (1 1 Q m-l; designed for temperatures of up to 1300 "C; Kantal) and ceramic isolation material (Kager).An NiCr-Ni thermo- couple (Heraeus) was attached to the surface of the quartz burner. Hydrogen was mixed with the helium stream about 2 cm before the burner inlet; air was supplied from the rear side of the burner. The furnace could be heated to 1200 "C by means of a variable transformer. The optimum tempera- ture was found to be 900 "C; the optimum flow rates were 40 ml min-' for hydrogen 60 ml min-' for air and 180 ml min-' for helium. The temperature of the cold trap and the quartz furnace were monitored by an Ahlborn Model 2280- 1 instrument connected to the thermocouples. The AAS monochromator was operated at 224.6 nm with a slit- width of 0.7 nm.The signal was recorded with a Shimadzu C-R3A Chromatopac integrator which was connected to the recorder outlet of the AAS instrument. Reagents and Standards Mono- di- and tributyl- and mono- di- and trimethyltin (MBT DBT TBT MMT DMT and TMT respectively) chlorides (Alfa-Ventron) and NaBEt (Strem) were used as received. Methanol was of analytical-reagent or 'for liquid chromatography' grade (Merck). Hydrochloric acid acetic acid and sodium acetate were of analytical-reagent grade (Merck). All other chemicals were of analytical-reagent grade or better. Organotin stock solutions were prepared at concentra- tions of approximately 1000 mg 1-l as tin in methanol. They were stored in the dark at 4 "C and remained stable for at least 6 months.I* A mixed organotin working solution was prepared daily by diluting the stock solution with water purified with a Milli-Q system (Millipore) to a range of approximately 20-80 pg 1-l as tin.A fresh solution of approximately 1% m/v NaBEt was prepared daily in Milli- Q-purified water and stored at 4 "C. A 1000 ml volume of acetic acid-sodium acetate buffer solution (pH 4.1) was obtained by mixing 800 ml of 0.2 mol 1-l acetic acid and 200 ml of 0.2 mol 1-l sodium acetate and stored in a polyethylene bottle at room temperature. Sediment Sampling Samples of surface river sediment were collected using a grab device from the river Main adjacent to Gr. Krotzen- burg and freeze-dried immediately on arrival in the laboratory. This sampling site was chosen because its sediments contain very low concentrations of organotin compoundsi8 and were therefore considered suitable to be used in a spiking experiment.In order to achieve better homogeneity and because the relationship between trace metal content and sediment particle size fraction is now well e~tablished,~~ the freeze-dried sample was sieved at 7 1 pm and the fine fraction was used in the subsequent experiments. Spiking of Sediment with MBT DBT and TBT A 100 g amount of freeze-dried sediment and 180 ml of Milli-Q-purified water were added to a 500 ml polycarbo- nate bottle. When the sediment was thoroughly soaked 3.143 ml of a mixed standard solution containing 13.7 12.0 and 32.0 mg 1-l as tin for MBT DBT and TBT respec- tively were added to the slurry and mixed well.The suspension was shaken and then kept in darkness for 10 d at room temperature to allow equilibration. The suspension was shaken twice each day during the period of equilibra- tion. After 10 d in darkness the spiked sediment was freeze- dried again. The theoretical concentrations of butyltins in the spiked sediment are listed in Table 1. Sediment Extraction Two different extraction solvents (methanolic hydrochloric acid and methanolic sodium hydroxide) were tested for the extraction of butyltin compounds from sediment. For extraction using methanolic HC1 0.5 mol 1-l HCl in methanol was used which was the optimum extraction solvent composition obtained for extracting a Rhine River sediment during previous work.31 For extraction using methanolic NaOH 0.5 mol 1-l NaOH in methanol was employed.Each sediment sample was extracted and ana- lysed in duplicate. Details of the extraction procedure are summarized in Fig. 1. Table 1 Concentrations of butyltin compounds in unspiked River Main sediment and theoretical concentrations of butyltins in River Main sediment after spiking Concentration/ng of Sn per gram of dry mass ~ ~~~~~ Sample BuSn3+ Bu2Sn2+ BujSn+ Unspiked 19.1 k 2.8 12.8 -e 3.4 ND* Spiked 448.6 f 2.8 388.3 k 3.4 1000 .o *ND = non-detectable (detection limit = 12 ng of Sn per gram of dry mass).JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 Centrifuge 20 min at 40009 121 ? Sediment (1 .Og) in polycarbonate (methanolic HCI) or glass (methanolic NaOH) bottle I 2 Centrifuge 20 min at 4000g Add methanolic HCI or methanolic NaOH Analysis using in situ ethylation cryogenic trapping and GC-AAS Procedure 1 (Methanolic NaOH) Separate supernatant and store in a 30 ml polycarbonate bottle - 1 c Procebure 3 (Methanolic HCI) 1 Adjust pH to 4.1 with 2.0 mol I-' NaAc 1 I Fig.1 Procedure for extraction of butyltin compounds from sediments with methanolic HCI and methanolic NaOH Analytical Procedure A 10 ml volume of acetate buffer and a Teflon-coated stirring bar were placed in the reaction vessel then a certain volume of the sample material (0.1-4.0 ml) and 130 pl of NaBEt solution were added. The reaction vessel was closed and secured with a stainless-steel clamp. The helium flow was switched to by-pass the reactor via a four-way valve and the reaction was continued for 14 rnin with magnetic stirring. The cold trap was cooled with liquid nitrogen to - 196 "C and the four-way valve was switched to pass helium through the reactor.After the solution had been purged for 9 min the helium flow was again switched to by- pass the reactor the liquid nitrogen removed and the integrator started. First the variable transformer heating the cold trap was set at 1.3 A for approximately 3.3 rnin to allow the column temperature to reach 120 "C. The trans- former was then turned up to 2.20 A so that the column attained a final temperature of 200 "C. The ethylated derivatives of methyltin and butyltin eluted within approxi- mately 4.0 min. Quantification Integrated absorbance values were used for quantitative calculation. Peaks in the gas chromatograms were assigned to individual organotin compounds on the basis of reten- tion time and were confirmed by standard additions.For the calculation of the concentrations of organotin com- pounds in sediment extracts three-point standard additions were made to eliminate or reduce the matrix effects. All analyses were carried out at least in duplicate. Results and Discussion Optimization of Ethylation Conditions Aqueous phase ethylation has previously been introduced as a practical derivatization m e t h ~ d . * ~ - ~ ~ The reaction conditions have also been optimized for methyllead and methylmercury determinations. In this work the amount of NaBEt reaction time and purge time are optimized. The integrated absorbance (peak area) was optimized for these three parameters by using a computer program33 based on a simplex algorithm.Commonly in hydride generation cryogenic trapping and GC-AAS experiments the reaction and purging are performed simultaneously and completed within about 4.5 min.18v31 In the present work however a single reaction step without helium flow through the reactor was added to ensure efficient ethylation of organotins. Thereafter purging of the ethylation products from the reactor with helium was carried out. This extra step is designed to compensate for the reaction rate of ethylation being slower than the hydride generation. A maximum purging time of 10 rnin was entered in the computer program to avoid blockage of the cold trap resulting from condensation of water vapour. The simplex optimization results are summarized in Table 2.For all of these simplex experiments 10 ml of buffer spiked to contain 5.7 3.9 3.7 3.8 3.6 and 1 1.5 ng as tin for MMT DMT TMT MBT DBT and TBT respectively were used as the test solution. Although a mixed standard was used in the optimization procedure the response of TBT alone was taken into account for the simplex experimental program i.e. the parameters were optimized only for TBT. As shown in Table 2 the amount of ethylation reagent added to the reactor is a significant parameter. When excessive reagent was added the response122 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 Table 2 Summary of simplex optimization experiments. Experiments were carried out on one day to take into account changes in instrument response Integrated absorbance? NaBEt,/ Reaction time/ Purge time/ Experiment No.PI* min min BuSn3+ Bu2Sn2+ BujSn+ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 *Volume of 1% m/v solution added. ?Arbitrary relative units. 50 168 168 522 325 246 50 50 50 58 126 12 122 260 10 19.4 12.4 12.4 13.1 13.5 14.2 14.3 8.6 9.4 13.4 13.4 12.2 4.0 4.9 7.8 4.9 5.3 5.4 5.7 5.7 6.3 6.2 9.0 9.0 7.4 8.6 298 1 2658 3077 1866 2219 204 1 1583 1427 1346 1239 1981 1496 1624 2127 2436 1996 2400 1406 1708 1809 2384 2242 2333 2156 2642 2345 2470 226 1 5252 4365 5518 3209 4007 4294 5969 564 1 5689 5164 5967 5844 5266 5063 to TBT decreased as in experiments 4 5 6 and 14. A similar result was obtained in the response of DBT. The exact reason for the signal reduction is not evident from the available data; however it is plausible that excessive addition of NaBEt results in excessive production of BEt which may interfere with the collection and elution of butylethyltin in and from the cold trap RpSn(4-p)+ + (4-p)NaBEt4-+ RpSnEt,,,,+(4-p)Na+ +(4-p)BEt3 where R=Me or Bu and p=O 1 2 or 3.Reaction time (1 0-1 9.4 min) and purging time (4-9 min) did not appear to affect the response systematically. From these data the optimum analytical parameters adopted were 130 11 of 1% m/v NaBEt in 10 ml of buffer reaction time 13.4 min and purge time 9 min. A typical chromatogram of mixed organotin standards obtained under these optimum conditions is shown in Fig. 2. A B 1 2 3 4 Time/m in Fig. 2 Chromatogram of a mixed organotin standard A Me3SnEt (2.5 ng as tin); B Me,SnEt (2.6 ng); C MeSnEt3 (3.8 ng); D Et,Sn (blank); E BuSnEt (2.6 ng); F Bu,SnEt (2.4 ng); and G Bu,SnEt (7.6 ng) Calibration and Detection Limit Calibration graphs for the six organotin species were obtained by introducing the same volume of mixed stan- dards at six different concentration levels into the reac- tion vessel followed by the ethylation and analysis proce- dure described above.The equations of the lines are given in Table 3. The absolute detection limit was deter- mined as 3 0 of baseline noise. The concentration detec- tion limit of the system for all organotin species was a function of the sample size. In this work 20 ml of buffer were used to obtain the calibration and the detection limit of this analytical procedure for six different organo- tin species is given in Table 3.The detection limits for environmental sediments depend on the volume of the extraction solvent and the amount added to the reactor. In general they are limited by interference resulting from the addition of large amounts of extractant. In compari- son with the hydride generation method the in situ ethylation technique described here has more potential to resist interference from environmental samples. Because no foaming takes place during derivatization a large amount of sample can be added to the reactor. The detection limits for this method when used for sediment analysis are given in Table 4. Analysis of River Sediment To assess better the reliability of the procedure spiked river sediment was used in the series of experiments described below.The recovery of organotin species from environmen- tal sediment and hence the accuracy are often difficult to assess in the absence of a suitable standard reference material (SRM). In this event the usual approach is to add a known amount of organotin to the sediment allow time for equilibration and then subject the spiked system to the analytical procedure. This approach has the disadvantage that spiking the sediment may not result in the same type or rate of organotin-sediment interaction as found in n a t ~ r e . ~ ~ J * However in the absence of a natural material with a known organotin content it is a reasonable approach to determine the efficiency of recovery. In this work two improvements to the procedure were made to improve the accuracy.Firstly the spiked sediment was kept at room temperature for 10 d instead of ~ v e r n i g h t ~ ~ * ~ ~ to allow better equilibration. Secondly a method based on extracting sediment with various volumes of solvent was employed toJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 123 Table 3 Equations of lines and limits of detection from calibration graphs of aqueous standards a Intercept Absolute Species absorbance)* Slope* r2 ng of Sn Me,Sn+ 1067 2736 0.9964 0.0 19 Me2Sn2+ 1096 2217 0.9985 0.023 MeSn3+ 974 960 0.9930 0.053 BuSn3+ 58.7 992 0.9920 0.05 1 Bu2Sn2+ -31.3 1004 0.9975 0.050 Bu3Sn+ 18.7 698 0.9979 0.073 (integrated b detection limit?/ *Arbitrary relative units. i n = 17. Procedure detection limit/ ng I-' of Sn 0.95 1.15 2.65 2.55 2.50 3.65 determine the true concentration of butyltin in the spiked sediment.The procedure suggested by Hellmann35 has been used by Schebek et al.34 to ascertain the trace content of organotin compounds in sediment cMM= CMiMi + CL VL (1) where true concentration of the analyte in the sedi- ment; M= mass of sediment; cMi = remaining concentration of the analyte in the sediment; Mi=mass of sediment after extraction; cL=concentration of analyte in the extraction solution; VL=volume of the extraction solution. Assuming a linear adsorption isotherm where all sites are equivalent then CMi = cLk where k is the adsorption constant. Also neglecting the difference between M and Mi eqn. (1) is rearranged to (2) As VL and M are known the true concentration of the analyte in the sediment (cM) can be calculated from the slope of the straight line obtained by plotting l/cL versus V,. If sufficient different extraction volumes are used in the experiment any possible deviation from linearity becomes readily apparent.Six pre-weighed samples of spiked sediment (1 .O g) were extracted with 15 30 45 60 80 and 100 ml of solvent in the following experiments. 1 /cL= ( VL/CM)M+ k/c Extraction with methanolic sodium hydroxide Methanol containing 0.5 moll-' NaOH was first employed to perform the procedure indicated as procedure I in Fig. 1. Results are given in Fig. 3. Clearly the assumption of the linear adsorption isotherm is valid only for TBT; MBT and DBT do not fit a linear equation. The true concentration 921 f 5 1 ng g-' dry mass as tin for TBT was calculated from the linear equation. In comparison with the spiked concentrations for butyltins given in Table 1 the recovery for TBT is 92 k 5%.~~~ ~~~~ ~ Table 4 Detection limits of butyltin species in River Main sediment matrix (30 of baseline noise) Absolute Procedure detection limit/ detection limit*/ Species ng of Sn ng of Sn g-I (dry mass) BuSn3+ 0.08 9 Bu2Sn2 + 0.34 38 BujSn+ 0.1 1 12 *45 ml of extraction solvent 0.4 mi of which was analysed. 1.5 1 v) .- I 0) - E > 1.0 E C .- c c 0.5 Y r - I 0 20 40 60 80 ioo Volume/ml Fig. 3 Results of extraction experiments with methanolic NaOH (procedure 1) W BuSn3+; A Bu2Sn2+; and 0 Bu3Sn+ 0 20 40 60 80 100 Vo I u m e/m I Fig. 4 Results of extraction experiments with methanolic HCI (procedure 2) BuSn3+; A Bu2Sn2+; and 0 Bu3Sn+ Extraction with methanolic hydrochloric acid Methanol containing 0.5 moll-' HCl was used in procedure 2 (Fig.1). Fig. 4 shows that MBT and DBT still do not fit a linear equation. For TBT an approximate linear relation- ship with a larger deviation at higher volume levels of solvent can be observed. In procedure 2 (Fig. I) the supernatant was separated by centrifugation after sonica- tion. Colloidal substances were produced when the pH of the supernatant was adjusted to 4.1 and they were difficult to eliminate even when another centrifuging step was added. These colloids were especially persistent when using higher volumes of extraction solvent. It was confirmed that they interfere with the yield of the ethylation reaction (see below) hence procedure 3 (Fig.l) was devised to eliminate them from the solution. Procedure 3 was simpler than procedure 2 because the pH was adjusted before centrifu-124 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 i Table 5 True concentrations of butyltin species in spiked River Main sediment - I I I - BuSn3+ Hu2Sn2+ Bu,Sn+ Procedure ct* R (O/o)t CI R (O/O) Cl R (Oh) 1 NLFS NLF NLF NLF 1047 f 259 104+26 2 132rt25 29+6 477 + 96 123+25 920+ 108 92+ 1 1 3 NLF NLF NLF NLF 921 +51 92+5 *c,= true concentration (ng g-l) calculated from eqn. (2). tR=recovery obtained (n=4) by comparison with the data in Table 1 SNLF = Non-linear fit. 5 0.8 c I 0 E 0.6 C 0 2 0.4 - \ .- c c 8 Vol u me/ml Fig. 5 Results of extraction experiments with methanolic HC1 (procedure 3) BuSn3+; A Bu,SnZ+; and 0 Bu3Sn+ gation.Hence the colloids were easily separated from the supernatant owing to coprecipitation with sediment parti- culates. Other operations in procedure 3 were the same as in procedure 2. The results are shown in Fig. 5 . As can be seen better linearity was obtained for MBT DBT and TBT using the improved procedure. The true concentrations and recoveries calculated from eqn. (2) for butyltin species are given in Table 5. Clearly the determination of butyltin species in sediment using the described ethylation method was affected mainly by two factors. The first is the chemical composition of the extracting solution and the way it affects extraction effici- ency. For example methanolic NaOH efficiently extracts TBT but not MBT and DBT.Methanolic HCl extracts TBT and DBT efficiently. These results were confirmed using the hydride generation te~hnique.’~ The second important factor is the interference of the sediment sample in the ethylation procedure. Two typical chromatograms obtained by procedures 2 and 3 with same volume of solvent ( 100 ml) and the addition of the same amount of analyte to the reaction vessel (3 ml) are shown in Fig. 6. Clearly a much better analytical result is achieved after eliminating the colloids. The data in Table 5 indicate that it is still difficult to determine MBT even when the ethylation method is used with extraction procedure 3. It should be noted however that the present ethylation parameters were optimized only for TBT response. In addition 0.5 moll-’ HC1 in methanol was the most efficient extractant for the extraction of TBT.A solvent of different composition was required for the efficient extraction of MBT and DBT.31 It is also possible that the lower recovery of MBT results from the centrifuga- tion during which MBT may be coprecipitated with colloids. From the above results it is clear that the variable extractant volume method is a reliable approach for the accurate determination of TBT and DBT in sediments. ( a J 1 I I I I 1 Ti m e/m i n 1 2 3 4 Fig. 6 Typical chromatogram for the analysis of spiked sediment. Using 100 ml of extraction solvent 3 ml of which were analysed (a) procedure 2; and (b) procedure 3. Peaks 1 BuSnEt,; 2 Bu2SnEt2; and 3 Bu,SnEt With respect to the colloids their bulk metal content was obtained by an inductively coupled plasma (ICP) method and is given in Table 6.The extraction of sediment with methanolic HC1 results in a solution containing a large number of organic substances and metals. Some metals e.g. iron(m) tend to form complexes with organic com- pounds in natural water and in a certain pH range they associate to form larger particles and become colloidal in character.” Table 6 Concentrations of various elements in the colloids determined by an ICP method Concentration/ Concentration/ mg g-l of dry mg g-’ of dry Element mass Element mass Sr Zn Fe Sb P Pb Ti V Cd Mn Cr Mo As 0.429 2.944 38.479 0.033 28.083 1.019 0.097 0.184 0.012 1 .ooo 0.263 0.034 0.056 Ni Be c o A1 K Zr Li Na Mg Ba Ca c u 0.2 10 0.008 0.022 19.079 1.099 0.026 0.0 17 122.736 2.776 1.016 49.666 1.101JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL.8 125 Evidently the separation of colloids by centrifugation does not result in a loss of TBT. To understand this interference with aqueous phase ethylation further work is needed to identify the molecular composition of the colloids. Conclusion The in situ ethylation cryogenic trapping and GC-AAS technique has been successfully applied to determine TBT and DBT in sediment. Advantages of the technique are as follows ( I ) the simplicity of the apparatus; (2) the handling procedure is kept to a minimum; (3) once formed the ethylated derivatives of organotins are more thermally stable than hydride derivatives; (4) preconcentration is achieved in situ and under an inert atmosphere; and (5) clean-up is effected by separating the ‘dirty’ liquid phase from the gaseous stream containing the derivatized ana- lytes.These factors combine to make this method an efficient approach for the determination of TBT and DBT in river sediments. For the determination of the recoveries of butyltins in sediment accurate results can be achieved by extracting with different volumes of solvent and calculating the true content of a compound from the slope of the reciprocal concentration against the volume of extraction solvent. In order to improve the reliability of the data application of the variable extraction volume method to determine the recovery and true content of organotins in sediments is suggested. To obtain a quantitative measurement for every butyltin compound in sediment the choice of an efficient extraction solvent is of paramount importance; it is believed that this has been accomplished for TBT.References 1 Maguire R. J. Appl. Organomet. Chem. 1987 1 475. 2 Kram M. L. Stang P. M. and Seligman P. F. Technical Report No. 1280 Naval Ocean Systems Center San Diego CA 1989. 3 Laughlin R. B. Jr. Linden O. and Guard H. E. Znt. Counc. Explor. Sea Bull. 1982 13 26. 4 Champ M. A. and Pugh W. L. Ocean’s 87 Proceedings 4 Marine Technology Society IEEE Ocean Engineering Society Halifax Nova Scotia September 29-October 1 1987 pp. 5 Huggett R. J. Unger M. A. Seligman P. F. and Valkirs A. O. Environ. Sci. Technol. 1992 26 232. 6 Fent K. Mar. Environ. Rex 1989 28 477. 7 Blair W. R. Olson G. J. Brinckman F.E. Paule R. C. and Becker D. A. Natl. Bur. Stand. (US) Rep. NBSIR-3321 1986. 8 Matthias C. L. Bellama J. M. Olson G. J. and Brinckman F. E. Environ. Sci. Technol. 1986 20 609. 9 Unger M. A. MacIntyre W. G. Greaves J. and Huggett R. J. Chemosphere 1986 15 46 1 . 10 Randall L. Donard 0. F. X. and Weber J. H. Anal. Chim. Acta 1986 184 197. 1296- 1308. 1 1 Maguire R. J. and Huneault H. J. Chromatogr. 1981 209 458. 12 Donard 0. F. X. Rapsomanikis S. and Weber J. H. Anal. Chem. 1986 58 772. 13 Miiller M. D. Fresenius’ Z. Anal. Chem. 1984 317 32. 14 Stephenson M. D. and Smith D. R. Anal. Chem. 1988 60 696. 15 Matthias C. L. Bellama J. M. Olson G. J. and Brinckman F. E. Int. J. Environ. Anal. Chem. 1989 35 61. 16 Stephenson M. D. Smith D. R. Hall L. W. Jr. Johnson W.E. Michel P. Short J. Waldock M. Huggett R. J. Seligman P. and Kola S. Ocean’s 87 Proceedings 4 Marine Technology Society IEEE Ocean Engineering Society Halifax Nova Scotia Canada September 29-October 1 1987 p. 1334. 17 Makkar N. S. Kronick A. T. and Cooney J. J. Chemosphere 1989 18 2043. 18 Schebek L. Andreae M. O. and Tobschall H. J. Environ. Sci. Technol. 1991 25 871. 19 Krone C. A. Brown D. W. Burrows D. G. Bogar R. G. Chan S. L. and Varanasi U. Mar. Environ. Res. 1989 27 1 . 20 Maguire R. J. Environ. Sci. Technol. 1984 18 291. 2 1 Fent K. Hunn J. and Sturm M. Naturwissenschaften 199 1 78 219. 22 Scott B. F. Chau Y. K. and Rais-Firouz A. Appl. Organo- met. Chem. 1991 5 151. 23 Lobinski R. Dirkx W. M. R. Ceulemans M. and Adams F. C. Anal. Chem. 1992 64 159. 24 Muller M. D. Anal. Chem. 1987 59 617. 25 Seligman P. F. Valkirs A. O. and Lee R. F. Ocean’s 86 Proceedings 4 Marine Technology Society Washington DC September 23-25 1986 p. 1189. 26 Desauziers V. Leguille F. Lavigne R. Astruc M. and Pinel R. Appl. Organomet. Chem. 1989 3 469. 27 Rapsomanikis S. Donard 0. F. X. and Weber J. H. Anal. Chem. 1986,58 35. 28 Rapsomanikis S. and Craig P. J. Anal. Chim. Acta 1991 248 563. 29 Ashby J. R. and Craig P. J. Sci. Total Environ. 1989 78 219. 30 Ashby J. R. and Craig P. J. Appl. Organomet. Chem. 1991 5 173. 31 Cai Y. Rapsomanikis S. and Andreae M. O. Mikrochim. Acta 1992 109 67. 32 Quevauviller P. and Donard 0. F. X . Appl. Organomet. Chem. 1990,4 353. 33 van der Wiel P. F. A. Kateman G. and Vandengiste B. G. M. Chemometric Optimization by Simplex Elsevier Amsterdam 1985. 34 Schebek L. Andreae M. O. and Tobschall H. J. Int. J. Environ. Anal. Chem. 1991 45 257. 35 Hellmann H. Fresenius’ 2. Anal. Chem. 1984 319 267. 36 Cai Y. Rapsomanikis S. and Andreae M. O. unpublished data. 37 Forstner H. and Wittmann G. T. W. Metal Pollution in the Aquatic Environment Springer Berlin 2nd edn. 198 1 pp. 214-2 16. Paper 2/03 704A Received July 13 I992 Accepted September 8 I992

ISSN:0267-9477    

DOI:10.1039/JA9930800119

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 127 Accurate Determination of Selenium in the Presence of Iron by Deuterium Arc Electrothermal Atomic Absorption Spectrometry Sunil Jai Kumar and S. Gangadharan Analytical Chemistry Division Bhabha Atomic Research Centre Bombay-400085 India A method is described which eliminates the over-correction due to spectral interference of iron on the total absorbance of selenium. A pyrolytic graphite platform was pre-treated with 1 mg ml-l of platinum and 5% m/v ascorbic acid solution. A 2 pl volume of a 1 mg ml-' palladium solution in 4% nitric acid and 0.5% m/v ascorbic acid was used to stabilize and enhance selenium sensitivity. A novel way of simultaneous introduction of palladium and ascorbic acid solutions without the precipitation of palladium is discussed.Palladium is found to delay atomization of selenium to temperatures of up to 1500 "C. Studies were carried out on 0.6 ng of selenium with varying amounts of iron in the furnace. For an absolute iron content of 40 pg in the furnace a recovery of 101 YO was obtained. The method was tested on a solution containing 50 ng ml-l of selenium in the presence of 2.5 mg ml-' of iron. The standard additions method was used to analyse the solution. A characteristic mass of 25 pg was obtained. Keywords Selenium determination; spectral interference due to iron; platinum-ascorbic acid pre-trea tment; electrothermal atomic absorption spectrometry; deuterium-arc background correction Iron is a major source of interference in the determination of selenium by electrothermal atomic absorption spectro- metry (ETAAS) with deuterium-arc background correc- t i ~ n .' - ~ The problem is associated with an over-correction due to spectral interference of iron at the 196.0 nm selenium wavelength. In general platinum has been used to remove this spectral interference; Peile et al.4 used carbon monoxide-platinum modification. Iron in the presence of oxygen forms FeO which according to these workers4 is responsible for the spectral interference. Carbon monoxide is added as an oxygen scavenger and platinum is believed to catalyse the reaction (2CO + 02-2C02). Bauslaugh et al.5 are of the view that platinum is sufficient to remove the interference by forming a platinum-iron alloy retarding the atomization of iron.Voth-Beach and Shradefl have used ascorbic acid and other reducing agents to reduce palladium to its elemental state for effective modification. A palladium-ascorbic acid mixed modifier has been used by Knowles and Brodie' using Zeeman-effect background correction in the determination of selenium in blood. Sampson* has determined selenium in serum with deuterium-arc background correction where the background absorption and atomic absorption are separated in time using a copper-magnesium modifier. In this work pyrolytic graphite platforms were pre-t reated with a platinum-ascorbic acid mixture to remove the spectral interference due to iron. The palladium-ascorbic acid modifier was used to stabilize and increase the selenium sensitivity. The method was developed to analyse selenium in water samples in the presence of 2.5 mg ml-' of iron.Table 1 instrumental conditions for the determination of sele- nium in the presence of iron Spectrometer- Background correction On Beam mode Double beam Wavelengthhm 196.0 Slit-width/nm 1 .o Slit-height Normal integration time/s 5.0 Lamp current/mA 10 Step No. Temperature/*C Time/s Argon/l min-' Graphite furnace- 110 110 1100 1100 110 110 2200 2200 2400 10 20-60 10 10 4.8 2.0 1.1 3.0 2.0 3.0 3.0 3.0 3.0 3.0 0 0 0 Read 3.0 Sampling- Sampling mode Automatic standard additions Volume of 200 ng ml-l Se/,ul 1-3 Volume of blanWp1 0-8 Volume of sample/,ul 5 Total volume delivered/,ul 10 Volume of palladium solution/pl 2 Experimental Instrumental Parameters A Varian Model AA-875 series spectrometer equipped with a GTA-95 graphite tube atomizer and an autosampler was used and deuterium-arc background correction was em- ployed.Eppendorff micropipettes were used for dilution. The details of furnace and spectrometer operating para- meters for the determination of selenium are shown in Table 1. A cooling step has been included in the ashing step to increase the size of the peak a~ea.~-ll Reagents Nitric acid. Suprapure Merck. Hydrochloric acid. Suprapure Merck. Selenium stock standard 2.5 mg ml-l. Prepared by dissolving high-purity selenium metal powder in nitric acid. Solution maintained in 5% v/v nitric acid. Palladium stock standard 1 mg ml-I. Prepared by dissolving palladium wire (99.97%) in nitric acid. Solution maintained in 4% v/v nitric acid.Platinum stock standard 1 mg ml-l. Prepared by dissolv- ing platinum wire (99.95%) in aqua regia [hydrochloric acid+nitric acid (4+ l)]. Final solution maintained in 5% v/v hydrochloric acid. Iron stock standard 10 mg ml-l. Prepared by dissolving high-purity iron in nitric acid. The final solution was maintained in 5% v/v nitric acid. Ascorbic acid general reagent grade. Ascorbic acid solu- tion (5% m/v) prepared by dissolving 250 mg of ascorbic128 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 Table 2 Furnace programme for platinum pre-treatment of the graphite platform Furnace temperature programme- Step No. Temperature/"C Time/s Argon11 min-' 1 2 3 4 5 6 7 8 9 10 110 110 250 1000 1000 110 110 2200 2200 2400 10 90 20 10 10 4.8 2.0 1.1 3.0 2.0 3.0 3.0 3.0 3.0 3.0 3.0 0 0 0 Read 3.0 Sampling- Sampling mode Automatic Volume of 1 mg m1-I of platinum solution/pl 10 10 Volume of 5Oh ascorbic acid solution/pl Multiple injection 20 No.of replicates 3 Last dry phase step 4 acid in 5 ml of freshly prepared de-ionized water. This was diluted ten times to prepare a 0.5% m/v ascorbic acid solution. Sample Preparation Selenium solution (200 ng ml-l) was prepared daily in 0.5% v/v nitric acid from dilution of the stock standard. Aliquots of 1 2 3 and 4 pl of 10 mg ml-l of iron solution corresponding to 10,20,30 and 40 pg absolute iron content respectively along with 3 pl of 200 ng ml-l of selenium solution (0.6 ng absolute selenium content) were introduced into the furnace for recovery tests. Selenium (50 ng ml-l) in 2.5 mg ml-l of iron was prepared from the stock solutions to check the validity of the method.A standard additions calibration graph was obtained by taking 1 2 and 3 pl of 200 ng ml-I of selenium standard and 5 pl of the sample solution in 0.5% ascorbic acid. A 2 p1 aliquot of 1 mg ml-l of palladium was used as modifier. An autosampler was used for the preparation of standards. Platform Pre-treatment The pyrolytic graphite was pre-treated by depositing 10 pl of 1 mg ml-l of Pt and 5% ascorbic acid each 20 times with the autosampler. The platform was heated in the graphite furnace under the conditions shown in Table 2. The entire procedure was repeated three times (overall 60 depositions) to obtain a lasting coating. A total volume of 20 pl was added for complete coverage of the platform surface.Care was taken to dry the solutions completely in the drying step. Results and Discussion Interference Due to Iron The baseline obtained in the presence of 20 pg of iron using a pyrolytic graphite platform in the absence of selenium is shown in Fig. 1 A. The negative dip in the baseline illustrates that the absorbance of the deuterium arc is greater than the total absorbance of the selenium hollow cathode lamp. This indicates the presence of a spectral interference as a result of which an over-corrected absor- bance of selenium is obtained (ie. total absorbance of selenium is lower than the actual value). The use of a platform pre-treated with platinum removes the spectral interference as a perfectly flat baseline is obtained (Fig.1 0.3 I 3000 0 3.0 Tirnels 6.1" Fig. 1 Traces of the selenium absorbance signal on the tempera- ture-time profile A 20 pg of iron on a pyrolytic graphite platform without selenium; B 20 pg of iron on a platform pre-treated with platinum and ascorbic acid without selenium; C 0.6 ng of selenium 2 pg of palladium and 10 pg of ascorbic acid on a platform pre-treated with platinum and ascorbic acid; and D 0.6 ng of selenium 2 pg of palladium 10 pg of ascorbic acid and 20 pg of iron on a platform pre-treated with platinum and ascorbic acid Table 3 Selenium recoveries with varying iron content in the furnace Recovery (O/o) Iron content/pg Selenium added/ng (n=4) 10 20 30 40 0.6 0.6 0.6 0.6 103 96.3 96.9 101 B) in the presence of 20 pg of iron without selenium.Peak shape due to 0.6 ng of selenium with a palladium-ascorbic acid mixed modifier in the absence of iron (Fig. 1 C) is similar to that in the presence of 20 pg of iron (Fig. 1 D) and has the same integrated absorbance. The recoveries of 0.6 ng of selenium with varying iron concentrations are compared in Table 3. Recoveries in the range of 96-103% were obtained for 10-40 pg of absolute iron content in the furnace. Ascorbic acid upon pyrolysis in the furnace is known to produce carbon monoxide and hydrogen. 12~13 The carbon monoxide produced along with platinum may be instru- mental in removing the overcorrection by acting as an oxygen scavenger which prevents the formation of Fe0.4 However a definite explanation regarding the actual mechanism of removal of this overcorrection requires further investigation.The relative standard deviation (RSD) obtained varied from 3 to 10%. The large RSD obtained even in the absence of iron is because the formation of selenium atoms depends on the surface properties of platinum deposited on the platform. These may not remain constant from one firing to the next. Hence there is a slight irregularity in the peak shapes obtained which affects the precision. Palladium-Ascorbic Acid Modification As platinum combines4 with selenium affecting its sensitiv- ity palladium-ascorbic acid modification has been used to stabilize and improve the selenium sensitivity. Palladium solution in the presence of ascorbic acid is readily reduced to elemental palladium even at room temperat~re.~.' Hence the sequence in which the palladium and ascorbic acid solutions are added is very important. The selenium absorbance is shown in Table 4 when ascorbic acid and palladium solutions are taken in by the autosampler capillary in the following sequences A ascorbic acid standard palladium solution; and B blank palladium solution standard ascorbic acid.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL.8 129 0.15 \ 8 e 2 % 0.1 (D 0 + z ' 0.05 m C Life of Pre-treated Platforms Pre-treatment of the platform with platinum and ascorbic acid by this method is found to have a lasting effect. For up to 200 firings there was no sign of any over-correction due to iron. Deterioration started only after 230 firings. The use of a small amount of platinum in each aliquot (10 pg) ensures a uniform and lasting coating.However the lifetime of the tube is affected by highly concentrated acidic solutions; the coating is removed by dissolution of platinum in acidic solutions. 1 I I I 1 I 1100 1300 1500 1700 1900 Ashing temperature (wall temperature)/"C Fig. 2 Effect of varying the ashing temperature on A 0.6 ng of selenium 2 pg of palladium 10 pg of ascorbic acid and 20 pg of iron on a pyrolytic graphite platform pre-treated with platinum and ascorbic acid; and B 0.6 ng of selenium and 2 pg of palladium on a pyrolytic graphite platform Results The method was tested on sample solutions containing 50 and 100 ng ml-I of selenium respectively and 2.5 mg ml-I of iron. Values of 49 and 103 ng m1-I were obtained with RSDs of 7.5 and 7.8% respectively for n= 3.The character- istic mass (amount of selenium giving an integrated absorbance of 0.0044 s) was found to be 25 pg. Table 4 Comparison of integrated absorbance for 0.6 ng of Se with sampling sequences A and B; (see Fig. 2 ) Absorbance Replicate Sequence 1 2 3 4 Mean RSD (Oh) A 0.080 0.076 0.056 0.056 0.067 19 B 0.118 0.129 0.124 0.132 0.125 5 In the case of sequence A the selenium absorbance continues to decrease with increasing number of replicate measurements (Table 4). For sequence B the absorbance remains constant with increasing number of replicate measurements. In sequence A ascorbic acid solution is taken into the capillary first and palladium last hence a large area of the capillary surface is contaminated by ascorbic acid and palladium solution remains in contact with this surface for the entire duration of its time in the capillary. This results in the deposition of palladium on the surface of the tip.While the solution is being delivered some of the selenium is withheld by palladium deposited on the tip of the capillary resulting in reduced absorbance. For sequence B the surface area contaminated by ascorbic acid is smaller and palladium solution comes in contact with this surface for a very short time (just while leaving the capillary). Therefore deposition of palladium does not occur resulting in a constant absorbance. No palladium precipitation was noticed on the tip for the entire duration of analysis for 2-5 p1 of 0.5% m/v ascorbic acid solution. For sequence A palladium deposited on the tip of the capillary can be removed by rinsing it with 20% v/v nitric acid for 3-4 min.A wash solution of 0.5% nitric acid is preferable for rinsing in between samplings by the autosam- pler. The effect of varying ashing temperature (wall tempera- ture) on the integrated absorbance due to 0.6 ng of selenium with platinum pre-treated platforms in the presence of 20 pg of iron 2 pg of palladium and 10 pg of ascorbic acid and with pyrolytic graphite platforms in the presence of 2 pg of palladium is shown in Fig. 2. Selenium loss in both cases starts at temperatures above 1500 "C which is close to the melting-point of palladium of 1554 OC.14 In the presence of ascorbic acid higher integrated absorbance is observed because of the effective reduction of palladium.6 Conclusion It has been shown that spectral interference due to iron is effectively removed by a novel method of pre-treating the platform with a platinum-ascorbic acid mixture.The method of pre-treatment is simple and does not require any additional reorganization to allow mixing of gases.4 The pre-treated platform was found to be effective for up to 200 firings in removing the over-correction due to iron. A novel method of simultaneous introduction of palladium and ascorbic acid solutions with an autosampler without palladium precipitation has been described. Use of a palladium-ascorbic acid mixed modifier permitted a higher ashing temperature. Interference-free determination of sele- nium in 2.5 mg ml-1 of iron solution has been demon- strated. 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 References Slavin W. and Carnrick G. R. At. Spectrosc. 1986 7 9 . Carnrick G. R. Manning D. C. and Slavin W. Analyst 1983 108 1297. Fernandez F. J. and Giddings R. At. Spectrosc. 1982 3 61. Peile R. Grey R. and Starek R. J. Anal. At. Spectrum. 1989 4 407. Bauslaugh J. Radziuk B. Saeed K. and Thomassen Y. Anal Chim. Acta 1984 165 149. Voth-Beach L. M. and Shrader D. E. J. Anal. At. Spectrum. 1987 2 45. Knowles M. B. and Brodie K. G. J. Anal. At. Spectrum. 1988 3 51 1. Sampson B. J. Anal. At. Spectrom. 1987 2 447. Falk H. Gilismann A. Bergann L. Minkwitz G. Schubert M. and Skole J. Spectrochim. Acta Part B 1985 40 533. Parsley D. H. J. Anal. At. Spectrum. 1991 6 289. Frech W. Li K. Berglund M. Baxter D. C. J. Anal. At. Spectrom. 1992 7 141. Gilchrist G. F. R. Chakrabarti C. L. and Byme J. P. J. Anal. At. Spectrom.,1989 4 533. Gilchrist G. F. R. Chakrabarti C. L. Byme J. P. and Lamoureux M. J. Anal. At. Spectrum. 1990 5 175. CRC Handbook of Chemistry and Physics ed. Weast R. C. CRC Press 70th edn. 1989-90 B-112. Paper 2/0 124 7B Received March 9 1992 Accepted June 15 1992

ISSN:0267-9477    

DOI:10.1039/JA9930800127

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 CUMULATIVE AUTHOR INDEX FEBRUARY 1993 Andreae Meinrat O. 119 Arpadjan Sonja 85 Botto Robert I. 51 Cai Yong 119 Canals Antonio 109 Corns Warren T. 71 Cortez Jesus Arroyo 103 Ebdon Les 71 Evans E. Hywell I Freedman Philip A. 19 Galley Paul J. 65 Gangadharan S. 127 Giglio Jeffrey J. 1 HernAndez Cdrdoba Manuel Hemandis Vincente 109 Hiefje Gary M. 65 Hill Steve J. 7 1 Hillamo Risto E. 79 Jarvis Kym E. 25 Karadjova Irina 85 Kojima Isao I15 Kondo Shinji I 1 5 Kumar Sunil Jai 127 L6pez Garcia Ignacio 103 Luong Van T. 41 103 Maenhaut Willy 79 Mazzetto G. 89 Milella E. 89 Ohlsson K. E. Anders 41 Pakkanen Tuomo A. 79 Platzner I. 19 Rapsomanikis Spyridon 1 19 Ren J. M. 59 Richner Peter 45 Ruiz Ana I. 109 Salin Eric D. 59 Sen Gupta Joy G. 93 Sentimenti E. 89 131 Sesi Norman N. 65 Stockwell Peter B. 71 Stroh Andreas 35 Sturgeon Ralph E. 41 Tserovsky Emil 85 Vollkopf Uwe 35 Walder Andrew J. 19 Williams John G. 25 Willie Scott N. 41 Wunderli Samuel 45

ISSN:0267-9477    

DOI:10.1039/JA9930800131

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 133 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY INSTRUCTIONS TO AUTHORS The Journal of Analytical Atomic Spectrometry (JAAS) is an international journal for the publication of original research papers communications and letters concerned with the development and analytical application of atomic spectrometric techniques. The journal is published bimonthly and also includes comprehensive reviews on specific topics of interest to practising atomic spec- troscopists and incorporates the literature reviews which were previously pub- lished in Annual Reports on Analytical Atomic Spectroscopy (ARAAS). Additional Special Conference Issues are also published. Manuscripts intended for publication as papers or communications must de- scribe original work related to atomic spectrometric analysis.Papers on all as- pects of the subject will be accepted including fundamental studies novel in- strument developments and practical analytical applications. As well as atomic absorption atomic emission and atomic fluorescence spectrometry papers will be welcomed on atomic mass spectrometry X-ray fluorescence/emission spec- trometry and secondary emission spectrometry. Papers describing the measure- ment of molecular species where these relate to the characterization of sources normally used for the production of atoms or concerning for example indirect methods of anlayses will also be acceptable for publication. Papers describing the development and applications of hybrid techniques involving atomic spec- trometry (e.g.GC coupled AAS and HPLC-ICP) will be particularly welcome. Manuscripts on other subjects of direct interest to atomic spectroscopists in- cluding sample preparation and dissolution and analyte preconcentration proce- dures as well as the statistical interpretation and use of atomic spectrometric data will also be acceptable for publication. Although short articles are acceptable the Society strongly discourages frag- mentation of a substantial body of work into a number of short publications. Unnecessary fragmentation will be a valid reason for rejection of manuscripts. There is no page charge for papers published in JAAS. The following types of papers will be considered. Original research papers. Communications which must be on an urgent matter and be of obvious scientific importance.Rapidity of publication is enhanced if diagrams are omitted but tables and formulae may be included. Communictions receive pri- ority and are usually published within 2-3 months of receipt. They are intended for brief descriptions of work that has progressed to a stage at which it is likely to be valuable to workers faced with similar problems. A fuller paper may be offered subsequently if justified by later work. Although publication is at the discretion of the Editor communications will be examined by at least one referee. Reviews which must be a critical evaluation of the existing state of knowl- edge on a particular facet of analytical chemistry. However original work may be included. Simple literature surveys will not be accepted for publication.It is desirable that potential review writers should contact the Editor before embark- ing on their work. Copyright. The whole of the literary matter (including tables figures dia- grams and photographs) in JAAS is Royal Society of Chemistry copyright and may not be reproduced without permission from the Society or such other owner of the copyright as may be indicated. Papers that are accepted must not be published elsewhere except by permission. Submission of a manu- script will be regarded as an undertaking that the same material is not being considered for publication by another journal in any language. European Associate Editor. Papers from Europe can be submitted lo Judith Egan-Shuttler Storchenweg 17 W-7772 Unteruhldingen Germany.US Associate Editor. Papers from North America can be submitted to Dr. J. M. Harnly US Department of Agriculture Beltsville Human Nutrition Research Center BLDG 161 BARC-EAST Beltsville MD 20705 USA. Manuscripts. Papers should be typewritten in double spacing on one side only of the paper. Copies of any related relevant unpublished material and raw data should be made available on request. Each table and illustration should be on a separate sheet at the end of the text; three copies of text and illustrations should be sent to the Editor JAAS The Royal Society of Chemistry Thomas Graham House Science Park Milton Road Cambridge CB4 4WF or directly to the US Associate Editor and a further copy retained by the author. Administration and Publication Procedure.Receipt of a contribution for consideration will be acknowledged immediately by the Editorial Office. The acknowledgement will indicate the paper reference number assigned to the con- tribution. Authors are particularly asked to quote this number on all subsequent correspondence. All papers (including conference presentations submitted for special issues) are sent simultaneously to at least two referees whose names are not disclosed to the authors. On the basis of the referees’ reports the Editor decides whether the paper is suitable for publication either unchanged or after appropriate revi- sion. This decision and relevant comments of the referees are communicated to the author. Differences of opinion are mediated by the Editor. possibly after consultation with further referees or in the last resort by the Editorial Board.When rejection of a paper is recommended the Editor informs the author and returns the top copy of the manuscript. Authors have the right to appeal to the Editorial Board if they regard a decision to reject as unfair. Authors will receive formal notification when papers are accepted for publi- cation. Proofs. The address to which proofs are to be sent should accompany the paper. Proofs should be carefully checked and returned immediately (by first class mail air mail or fax). Particular attention should be paid to numerical data both in the tables and text. Reprints. Fifty reprints of each paper are supplied free on request. Additional reprints can be purchased if ordered at the time of publication.Details are sent to authors with the proofs. Notes on the Writing of Papers for JAAS Manuscripts should be in accordance with the style and usage shown in re- cent copies of JAAS. Conciseness of expression is expected clarity is increased by adopting a logical order of presentation with suitable paragraph or section headings. Spellings should be in accordance with the Oxford English Dictionary. To facilitate abstracting and indexing by Chemical Abstracts Service and other abstracting organizations it would be helpful if at least one forename could be included with each author’s family name. The corresponding author should be clearly indicated. Descriptions of methods should be supported by experimental results show- ing accuracy precision and selectivity.The recommended order of presentation is as indicated below ( a ) Tirle. This should be as brief as is consistent with an adequate indication of the original features of the work. The title should usually include the analyte being determined or identified the matrix and the analytical method used. ( b ) Summary. A summary of about 250 words giving the salient features and drawing attention to the novel aspects should be provided for all pa- pers. It should be essentially independent of the main text and include relevant quantitative information such as detection limits precision and accuracy data. ( c ) Keywords. Up to five keywords or key phrases indicating the topics of importance in the work described should be included after the summary. (6) Aim of investigation.A concise introductory statement of the novel fea- tures of the work and the object of the investigation with any essential historical background followed if necessary by a brief account of pre- liminary experimental work with relevant references. ( e ) Description of the experimental procedures. Working details must be given concisely. Analytical procedures should be given in the form of instructions; well known operations should not be described in detail. Suppliers of equipment and materials and their locations should be mentioned. (f) Results and Discussion. Results are best presented in tabular or diagram- matic form (but not both for the same results) followed by an appropri- ate statistical evaluation which should be in accordance with accepted practice.For example a new procedure for multi-element determinations which produced results for which the concentration of 8 out of 10 of the elements determined in a standard reference material were statistically134 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY I993 indistinguishable from the certificate values should be described in those terms and not referred to as ‘excellent agreement’. This is particularly important in the summary. Any discussion should comment on the scope of the method and its validity followed by a statement of any conclusions drawn from the work. A separate conclusions section is not encouraged but if included it should not simply duplicate state- ments in the discussion. (g) Acknowledgements. Contributions other than co-authors companies or sponsors may be acknowledged in a separate paragraph at the end of the paper.Titles may be given but not degrees. ( h ) References. References should be numbered serially in the text by means of superscript figures e.g.. Foote and Delves,’ Burns et al.2 or ... in a recent paper . . . I and collected in numerical order under ‘References’ at the end of the paper. They should be listed with all the authors’ names and initials in the following form (double-spaced typing) Yerian T. D. Christian G. D. and Riiieka J. Analyst 1986 111 865. Sharp B. L. Barnett N. W. Burridge J. C. Littlejohn D. and Tyson J. F. J. Anal. At. Spectrum. 1988,3 133R. Committee for Analytical Methods for Residues of Pesticides and Veterinary Products in Foodstuffs and the Working Party on Pesticide Residues of the Ministry of Agriculture Fisheries and Food Analyst 1985,110,765.Hara H. Horvai G. and Pungor E. Analyst 1988 113 1817; Anal. Abstr. 1989,51 6H57. Norwitz G. and Keliher P. N. Analyst 1987 112 903 (and references cited therein). L’vov B. V. Polzik L. K. Romanova N. P. and Yuzeforskii A. I. J. Anal. At. Spectrom. in the press. O’Connor A Sigma St. Louis MO personal communication 1989. Appelqvist R. Ph. D. Thesis University of Lund Sweden 1987. Bi C. Evans E. H. and Caruso J. A. paper presented at the 1992 Winter Conference on Plasma Specctrochemistry San Diego CA USA January 6-1 I 1992. Journal titles should be abbreviated according to the Chemical Abstracts Service Source Index (CASSI). The abbreviation for this journal is J. Anal.At. Spec trom. For books the edition (if not the first) the publisher and the place and date of publication should be given followed by the page number. Harrison W. W. and Donohue D. L. in Treatise on Analytical Chemistry eds. Kolthoff 1. M. and Winefordner J. D. Wiley New York 2nd edn. Gutscht. C. D. Calixarenes Royal Society of Chemistry Cambridge 1989. British Pharmacopoeia 1988 HM Stationery Office London 1988 vol. I p. 140. Riiicka J. and Hansen E. H. Flow Injection Analysis 2nd edn. Wiley New York 1988 pp. 299-304. Moody G. J. and Thomas J. D. R. in Ion Selective Electrodes in Analytical Chemistry ed. Freiser H. Plenum New York 1978 ch. 4. Beauchemin D. and Craig J. M. in Plasma Source Mass Spectrometry. The Proceedings of the Third Surrey Conference on Plasma Source Mass Spectrometry University of Surrey July 16th-I9th 1989 eds.Jarvis K. E. Gray A. L. Jarvis I. and Williams J. G. The Royal Society of Chemistry Cambridge 1990 pp. 25-42. Official Methods of Analysis of the Association of Oficial Analytical Chemists ed. Horwitz W. Association of Official Analytical Chemists Arlington VA 13th edn. 180 sect. 20.104. 1989 Pt. 1 VOI. I I ch. 3. pp. 189-235. Authors must in their own interest check the lists of references against the original papers; second-hand references are a frequent source of error. References to conference abstracts which have not been published in the open lit- erature are not acceptable. The number of references must be kept to a minimum. Nomenclature. Current internationally recognized (IUPAC) chemical nomen- clature should be used.Common trivial names may be used but should first be defined in terms of IUPAC nomenclature. A listing of all relevant IUPAC nomenclature publications appears in the February issue. Symbols and units. The SI system of units as recommended by IUPAC should be followed. Their basis is the ‘Systbme Internationale d’Unit6s’ (SI). A detailed treatment is given in the ‘Green Book’ Quantities Units and Symbols in Physical Chemistry (Blackwell Oxford 1988 edn.). The following will be the guidelines used ( a ) A metric system will always be used in preference to a non-metric one. (b) SI will be the standard usage. ( c ) The units used to record the definitive values of ‘critical data’ or quanti- ties measured to a high degree of accuracy will be SI.These units are summa- rized in the Appendix. The effect on current style of papers for JAAS includes the following ( a ) dimensions should preferably be given in metres (m) or in millimetres ( b ) temperatures should be expressed in K or “C (not OF); ( c ) wavelengths should be expressed in nanometres (nm) not m l (d) frequency should be expressed in Hz (or kHz etc.) not in c/s or c.P.s.; rotational frequency can be denoted by use of s-l; in mass spectrometry signal intensity should be expressed in counts s-I and not in Hz; (mm); ( e ) radionuclide activity should be expressed in becquerels (Bq); (f) the micron (p) will not be used; 10” will be 1 p . When non-SI units are used they must be adequately explained unless their definition is obvious (e.g.“C and A). The derivation of derived non-SI units should be indicated. Abbreviations. Abbreviational full stops are omitted after the common contractions of metric units (e.g. ml g pg mm) and other units represented by symbols. Abbreviations other than those of recognized units should be avoided in the text except after definition. Upper case letters without points should be used for abbreviations for techniques and associated terms subsequent to defini- tion e.g. HPLC AAS XRF UV NMR SCE. Other common abbreviations and contractions require full points e.g. eqn. m.p. Dr. except when sub- or super-script kx for example. The abbreviations Me Et PP Bun Bul Bu. But Ph Ac Alk Ar and Hal can be used; others should be defined. Carboxy groups are written CO?R not COOR.Substituents should be indicated by R (one) or by R’ R’ R’ ... (more than one). Percentage concentrations of solutions should be stated in internationally recognized terms. Thus the symbols ‘m’ instead of ‘w’ for mass and ‘v’ for vol- ume are to be used. The following show the manner of expressing these per- centages together with an acceptable alternative given in parentheses % m/m (g per 100 g); % m/v (g per 100 ml); % v/v. Further implications of the use of the term ‘mass’ are that ‘relative atomic mass’ of an element (A,) replaces atomic weight and ‘relative molecular mass’ of a substance (M,) replaces molecular weight. Concentrations of solutions of the common acids are often conveniently given as dilutions of the concentrated acids such as ‘dilute hydrochloric (1 +4)’ which signifies 1 volume of the concentrated acid mixed with 4 volumes of water.This avoids the ambiguity of 1 4 which might represent either I + 4 or 1 + 3. Dilutions of other solutions should be expressed in a similar manner. Molarity is generally expressed as a decimal fraction (e.g. 0.375 mol dm-’). Tables and diagrams. Table column headings should be brief. Tables con- sisting of only two columns can often be arranged horizontally. Tables must be supplied with titles and be so set out as to be understandable without reference to the text. Either tables or graphs may be used but not both for the same set of results unless important additional information is given by so doing. The information given by a straight-line calibration graph can usually be conveyed adequately as an equation or statement in the text.Column headings and graph axis labels should be in accord with SI conven- tions. Thus the expression of numerical values of a physical quantitiy should be dimensionless i.e. the quotient of the symbol for the physical quantity and the symbol for the unit used e.g. p/Pa or some mathematical function of a number e.g. In @/Pa). Further examples are v/cm-l Ucm mass of substance/g and flow rate/ml min-’. For units which are already dimensionless. i.e. ratios such as % or ppm the type of ratio is indicated in parentheses e.g. e (%) or e (ppm). The diagonal line (solidus) will not be used to represent ‘per’. In accor- dance with the SI system units such as grams per millilitre are already ex- pressed in the form g mi-’.It should be noted that the ‘combined’ unit g mi-’ must not have any ‘intrusive’ numbers. To express concentration in grams per 100 millilitres the word ‘per’ will still be required Concentratiodg per 100 ml. It may be preferable for an author to express concentrations in grams per litre (g I-’) rather than grams per 100 ml.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 135 Most diagrams will be retraced and lettered in order to achieve uniform line thickness and lettering size and style. However all diagrams should be carefully and clearly drawn on good quality paper and should be carefully and clearly lettered. If possible chromatograms and spectra complicated flow charts circuit digrams etc. should be supplied as artwork for direct reproduction in order to avoid time-consuming and expensive redrawing. The clearest copy should be without lettering.Three complete sets of illustrations should be provided two sets of which may be made by any convenient copying process for transmission to the referees. All diagrams should be accompanied by a separately typed set of cap- tions. Wherever possible extensive identifying lettering should be placed in the caption rather than on lines on graphs etc. Photographs. Photographs can be submitted if they convey essential in- formation that cannot be shown in any other way. They should be submitted as glossy or matt prints made to give the maximum detail. Colour pho- tographs will be accepted only when a black-and-white photograph fails to show some vital feature and can be supplied either as prints or transparen- cies.Appendix I The SI System of Units In the SI system there are seven base units- Symbol for Name Symbol Physical quantity quantity of unit for unit length I metre m time t second S mass m kilogram kg electric current I ampere A thermodynamic temperature T kelvin K amount of substance n mole mol luminous intensity I candela cd There are two supplementary dimensionless units for plane angle (radian rad) and solid angle (steradian sr). Some derived SI units that have special names are as follows- Name Symbol Physical of unit for unit Definition of unit frequency force pressure stress energy work heat power electric charge electric potential electric capacitance electric resistance electric conductance magnetic flux magnetic flux density inductance Celcius temperature plane angle solid angle hertz newton pascal joule watt coulomb volt farad ohm siemens weber tesla henry degree Celsius radian steradian Hz N Pa J W C V F R S Wb T H "C rad sr Examples of other derived SI units with no special names or symbols are- Physical quantity SI unit area volume density velocity angular velocity acceleration pressure kinematic viscosity diffusion coefficient dynamic viscosity electric field strength magnetic field strength luminance square metre cubic metre kilogram per cubic metre metre per second radian per second metre per second squared newton per square metre square metre per second newton second per square metre volt per metre ampere per metre candela per square metre Certain units will be allowed in conjunction with the SI system e.g.- Symbol Physical quantity Name of unit for unit time plane angle volume magnetic flux density (magnetic induction) temperature t energy pressure mass minute degree litre gauss degree Celsius electronvolt bar unified atomic mass unit min 1 G "C eV bar 0 U Symbol for SI unit m' m" k m-' m s-I rad s-' m s-' N m-' m2 s-I N s m-? V m-' A m-' cd m-' Definition of unit 60s (dl80) rad lo-' T 1.602 1 x lo-" J los Pa I .660 54 x lo-" kg lo-' m' = dm3 tl°C = TIK - 273.16136 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 The other common units of time (e.g. hour and day) will continue to be used in appropriate contexts.Decimal multiples and submultiples have the following names and symbols (for use as prefixes)- lo-' 10" I 0-' lo-" 1 0-l5 10- lo-" 10-24 milli micro nano pic0 femto atto zepto yocto 1 0' I O6 10' 1 O'? 1 0lS 10'" 10" I 0 2 4 kilo mega gigs tera pe ta exa zetta yotta k M G T P E Z Y Compound prefixes (e.g.mpm) should not be used; lo-' m = 1 nm. Appendix II Abbreviations Whenever suitable elements may be referred to by their chemical symbols and compounds by their formulae. fined at the first place of mention. The following abbreviations will be used extensively in the Atomic Spectrometry Updates and may be used in original papers provided that they are de- a.c. AA AAS AE AES AF AFS AOAC APDC ASV CCP CMP CRM cw d.c. DCP DDDC DMF DNA EDL EDTA EDXRF EIE EPMA ETA ETAAS ETV EXAFS FAAS FAB FAES FAFS FI FPD FT FTMS GC GD GDL GDMS Ge (Li) HCL h.f.HG HPGe HPLC IAEA IBMK ICP ICP-MS IR IUPAC alternating current atomic absorption atomic absorption spectrometry atomic emission atomic emission spectrometry atomic fluorescence atomic fluorescence spectrometry Association of Official Analytical Chemists ammonium pyrrolidinedithiocarbamate (ammonium pyrrolidin- 1 -yl anodic-stripping voltammetry capacitively coupled plasma capacitively coupled microwave plasma certified reference material continuous wave direct current d.c. plasma diammonium diethyldithiocarbamate N N-dimethylformamide deoxyribonucleic acid electrodeless discharge lamp ethylenediaminetetraacetic acid energy dispersive X-ray fluorescence easily ionizable element electron probe microanalysis electrothermal atomization electrothermal atomic absorption spectrometry electrothermal vaporization extended X-ray absorption fine structure spectroscopy flame AAS fast atom bombardment flame AES flame AFS flow injection Flame photometric detector Fourier transform Fourier transform mass spectrometry gas chromatography glow discharge glow discharge lamp glow discharge mass spectrometry lithium-drifted germanium hollow cathode lamp high frequency hydride generation high-purity germanium high-performance liquid chromatography International Atomic Energy Agency isobutyl methyl ketone (4-methylpentan-2-one) inductively coupled plasma inductively coupled plasma mass spectrometry infrared International Union of Pure and Applied Chemistry dithioformate) LA LC LEAFS LEI LMMS LOD LTE MECA MIP MS NAA NaDDC NIES NIST NTA OES PIGE PIXE PMT PPm PTFE QC r.f.REE( s) RIMS RM RSD SIB SEC SEM SFC Si(Li) SIMAAC SIMS SIN SR SRM SSMS STPF TCA TIMS TLC TOP0 TXRF u.h.f. uv VDU vuv WDXRF XRF PPb laser ablation liquid chromatography laser-excited atomic fluorescence spectrometry laser-enhanced ionization laser microprobe mass spectrometry limit of detection local thermal equilibrium molecular emission cavity analysis microwave-induced plasma mass spectrometry neutron activation analysis sodium diethylidithiocarbamate National Institute for Environmental Studies National Institute of Standards and Technology nitrilotriacetic acid optical emission spectrometry particle-induced gamma-ray emission particle-induced X-ray emission photomultiplier tube parts per billion parts per million pol ytetrafluoroeth y lene quality control radiofrequency rare earth element(s) resonance ionization mass spectrometry reference material relative standard deviation signal to background ratio size-exclusion chromatography scanning electron microscopy supercritical fluid chromatography lithium-drifted silicon simultaneous multi-element analysis with a continuum source secondary ion mass spectrometry signal to noise ratio synchrotron radiation Standard Reference Material spark source mass spectrometry stabilized temperature platform furnace trichloroacetic acid thermal ionization mass spectrometry thin- layer chromatography trioctylphosphine oxide total reflection X-ray fluorescence ul tra-high-frequenc y ultraviolet visual display unit vacuum ultraviolet wavelength dispersive X-ray fluorescence X-ray fluorescence The Royal Svciety of Chemistty Thomas Graham House Science Park Milton Road Cambridge UK CB4 4 WF. Telephone +44 (0)223 420066; Fax +44 (0)223 420247; E-mail RSC09 @ UK.AC.RL.GB (JANET)

ISSN:0267-9477    

DOI:10.1039/JA9930800133

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 137 JOURNALS OF THE ROYAL SOCIETY OF CHEMISTRY Refereeing Procedure and Policy (1993) 1.0 Contributions to Dalton Perkin and Faraday Transactions J. Mater. Chem. The Analyst J. Anal. At. Spectrom. and J. Chem. Research 1.1 Introduction This document summarises the procedure used for assessing papers submitted to the four Transactions J. Mater. Chem. The Analyst J. Anal. At. Spectrom. and J. Chem. Research and provides guidelines for referees engaged in this assessment. 1.2 Subject matter Papers are submitted to the various journals according to subject matter. If it is felt that a paper would be published more appropriately in an RSC journal other than the one suggested by the author the referee should inform the Editor.The topics covered by the various journals are as follows. Dalton Transactions (Inorganic Chemistry). All aspects of the chemistry of inorganic and organometallic compounds including bioinorganic chemistry and solid-state inorganic chemistry; the applications of physicochemical techniques to the study of their structures properties and reactions including kinetics and mechanism; new or improved experimental techniques and syntheses. Faraday Transactions (Physical Chemistry and Chemical Physics). Gas-phase kinetics and dynamics; molecular beam kinetics and spectroscopy photochemistry and photophysics; energy transfer and relaxation processes laser-induced chemistry; spectroscopies of molecules molecular and gas- phase complexes quantum chemistry and molecular structure statistical mechanics of gaseous molecules and complexes; spectroscopies statistical mechanics and quantum theory of the condensed phase computational chemistry and molecular dynamics; colloid and interface science surface science physisorption and chromatographic science chemisorption and heterogeneous catalysis zeolites and ion-exchange phenomena; electrode processes liquids and solutions; solid-state chemistry (microstructures and dynamics); reactions in condensed phases; physical chemistry of macromolecules and polymers; materials science; thermodynamics; biophysical chemistry and radiation chemistry. Perkin Transactions 1 (Organic Chemistry).All aspects of organic and bio-organic chemistry. These include synthetic organic chemistry of all types organometallic chemistry chemistry and biosynthesis of natural products the relationship between molecular structure and biological activity the chemistry of polymers and biological macromolecules and medicinal and agricultural chemistry where there is originality in the science.Perkin Transactions 2 (Physical Organic Chemistry). Physicochemical aspects of organic organometallic and bio- organic chemistry including kinetic mechanistic structural spectroscopic and theoretical studies. Such topics include structure-activity relationships and physical aspects of biological processes and of the study of polymers and biological macromolecules. Journal of Materials Chemistry. The chemistry of materials particularly those associated with advanced technology; modelling of materials; synthesis and structural characteris- ation; physicochemical aspects of fabrication; chemical structural electrical magnetic and optical properties; applic- ations.The Analyst (Analytical Chemistry). Theory and practice of all aspects of analytical chemistry fundamental and applied inorganic and organic including chemical physical and biological methods. Journal of Analytical Atomic Spectrometry. The develop- ment and analytical application of atomic spectrometric techniques. Journal of Chemical Research. All areas of chemistry. The format of this journal (one- or two-page printed synopsis in Part S plus microform version of authors’ full text typescript in Part M) makes it particularly suitable for papers containing lengthy experimental sections or extensive data tabulations. 1.3 Procedure Each manuscript is considered independently by two referees. The referees’ reports constitute recommendations to the appropriate Editorial Board which is empowered to take final action on manuscripts submitted. The Editor acting for the Editorial Board is responsible for all administrative and executive actions and is empowered to accept or reject papers.It is the Editor’s duty to see that as far as possible agreement is reached between authors and referees; although the referees may need to be consulted again concerning an author’s reply to comments further refereeing will be avoided as far as possible. 1.3.1 Adjudication of disagreements. If there is a notable discrepancy between the reports of the two referees or if the difference between authors and referees cannot be resolved readily a third referee may be appointed as adjudicator.In extreme cases differences may be reported to the appropriate Editorial Board for resolution. When a paper is recommended for rejection by referees the Editor will inform the authors and return the top copy of the manuscript. Authors have the right to appeal to the Editorial Board if they regard a decision to reject as unfair. The Editor may refer to the Editorial Boards any papers which have been recommended for acceptance by the referees but about which the Editor is doubtful. 1.3.2 Anonymity. The anonymity of referees is strictly preserved and reports should be couched in terms which do not disclose the identity of the writer. A referee should never communicate directly with an author unless and until such action has been sanctioned by the Society through the Editor.1.3.3 Conjidentiality. A referee should treat a paper received for assessment as confidential material. Information acquired138 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 by a referee from such a paper is not available for citation until the paper is published. 1.4 Policy The primary criterion for acceptance of a contribution for publication is that it should advance scientific knowledge significantly. Papers that do not contain new experimental results may be considered for publication only if they either reinterpret or summarise known facts or results in a manner presenting an advance in chemical knowledge.Papers in interdisciplinary areas are acceptable if the chemical content is considered satisfactory. Papers reporting results regarded as routine or trivial are not acceptable in the absence of other desirable attributes. Although short papers are acceptable the Society strongly discourages the fragmentation of a substantial body of work into a number of short publications; such fragmentation is likely to be grounds for rejection. The length of an article should be commensurate with its scientific content; however authors are allowed every latitude (consistent with reasonable brevity) in the form in which their work is presented. Figures and flow-charts can often save space as well as clarify complicated arguments and should not be excised unless they are unhelpful or really extrava- gant.If a paper as a whole is judged suitable for the Journal minor criticisms should not be unduly emphasised. It is the responsibility of the Editor to ensure the use of reasonably brief phraseology and to assist the author to present his work in the most appropriate format. However referees should not hesitate to recommend rejection of papers which appear incurably badly composed. It should be clearly understood that referees’ reports are made in confidence to the Editor at whose discretion comments will be transmitted to the author. To assist the Editor referees are requested to indicate which comments are designed only for consideration as distinct from those which in the referee’s view require specific action or an adequate answer before the paper is accepted.Referees may ask for sight of supporting data not submitted for publication or for sight of a previous paper which has been submitted but not yet published. Such requests must be made to the Editor not directly to the author. 1.4.1 Authentication of new compounds. Referees are asked to assess as a whole the evidence in support of the homogeneity and structure of all new compounds. No hard and fast rules can be laid down to cover all types of compounds but the Society’s policy is that evidence for the unequivocal identification of new compounds should wherever possible include good elemental analytical data; for example an accurate mass measurement of a molecular ion does not provide evidence of purity of a compound and must be accompanied by independent evidence of homogeneity.Low-resolution mass spectrometry must be treated with even more reserve in the absence of firm evidence to distinguish between alternative molecular formulae. Where elemental analytical data are not available appropriate evidence which is convincing to an expert in the field may be acceptable. Spectroscopic information necessary to the assignment of structure should normally be given. Just how complete this information should be must depend upon the circumstances; the structure of a compound obtained from an unusual reaction or isolated from a natural source needs much stronger supporting evidence than one derived by a standard reaction from a precursor of undisputed structure. Referees are reminded of the need to be exacting in their standards but at the same time flexible in their admission of evidence.It remains the Society’s policy to accept work only of high quality and to permit no lowering of stand- ards. 1.5 Titles and summaries Referees should comment on titles and summaries with the following points in mind. Titles of papers are used out of context by several organisations for current awareness purposes. To enable such systems to serve chemists adequately titles must be written around a sufficient number of scientific words carefully chosen to cover the important aspects of the paper. Summaries should preferably be self-contained so that they can be understood without reference to the main text. 1.6 Speed of Refereeing The Editorial Boards are anxious to maintain and to reduce further if possible the publication times now being achieved.In this connection referees should submit their reports with the minimum of delay or return manuscripts immediately to the Editor if long delay seems inevitable. 1.7 Suggestion of Alternative Referees The Editor welcomes suggestions of alternative referees competent to deal with particular subject areas. Such suggestions are particularly helpful in cases where referees consider themselves ill-equipped (in terms of specialist knowledge) to deal with a specific paper and in highly specialized or new areas of research where only a limited number of experts may be available. If in such a case the alternative and the original referee work in the same institution the manuscript may be passed on directly after informing the Editor.1.8 Short Papers and Letters ‘Short Papers’ are published in J. Chem. Research. They are intended for the description of essentially complete pieces of work which can be described in two printed pages or less. They are NOT preliminary communications nor in any way an alternative to Chemical Communications for which there are additional criteria of novelty and urgency. The quality of material contained in a short paper should be the same as that in a full paper. Investigations arising out of some larger project but not prosecuted to the same degree are particularly appropriate for this format. A short paper should not normally exceed in length about 8 pages of typescript including figures tables etc. It should comprise a one-sentence abstract and discussion but adequate experimental details are required.As a consequence of its length it appears in full in Part S with no microform version in Part M. ‘Letters’ published only in Dalton Transactions are a medium for the expression of scientific opinions and views normally concerning material published in that journal; it is intended that contributions in this format should be published rapidly. The letters section is for scientific discussion and is not intended to compete with media for the publication of more general matters such as Chemistry in Britain. Only rarely should a Letter exceed one printed column in length (about 1-2 pages of typescript). Where a letter is polemical in nature and if it is accepted a reply will be solicited from other parties implicated for consideration for publication alongside the original letter.1.9 Relationship with Communications Journals In cases where a preliminary report of the work described has appeared (for example in Chemical Communications) refereesJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 139 should alert the editor to any excessive and unnecessary repetition of material; this can arise in connection with communications journals in which the restrictions on length and the reporting of experimental data are less severe than those of Chemical Communications. Furthermore the acceptability of the full paper must be judged on the basis of the significance of the additional information provided as well as on the criteria outlined in the foregoing sections.2.0 Contributions to Chemical Communic- ations Chemical Communications is intended as a forum for preliminary accounts of original and significant work in any area of chemistry that is likely to prove of wide general appeal or exceptional specialist interest. Such preliminary reports should be followed up in most cases by full papers in other journals providing detailed accounts of the work. It is Society policy that only a fraction of research work warrants publication in Chemical Communications and strict refereeing standards should be applied. The benefit to the reader from the rapid publication of a particular piece of work before it appears as a full paper must be balanced against the desirability of avoiding duplicate publication.The needs of the reader not the author must be considered and priority in publication should not be allowed to determine acceptability. Acceptance should be recommended only if in the opinion of the referee the content of the paper is of such urgency that rapid publication will be advantageous to the progress of chemical research. The length of Communications is strictly limited; only in exceptional circumstances should it exceed one printed page (two-and-a-half to three A4 pages of typescript) and referees should be particularly critical of manuscripts longer than this. Communications do not contain extensive spectroscopic or other experimental data but referees may ask for sight of such data before reaching a decision. The refereeing procedure for Communications is the same as that for full papers except that rapidity of reporting is crucial in order to maintain rapid publication. The Journals Committee functions as the Editorial Board of Chemical Communications and as such acts as final arbiter in cases of dispute.3.0 Communications submitted to The Analyst and J. Anal. At. Spectrom. Criteria for acceptance of communications submitted to The Analyst and J. Anal. At. Spectrom. are similar to those for contributions to Chemical Communications except that they should be concerned specifically with analytical chemistry. However communications to The Analyst and J. Anal. At. Spectrom. are not subjected to refereeing in the usual way; a decision whether or not to publish rests with the Editor who may or may not obtain advice from a referee.4.0 Communications submitted to Perkin Dalton or Faraday Transactions or J. Mater. Chem. Criteria for acceptance of Communications submitted to Perkin Dalton or Faraday Transactions or J. Mater. Chem. are similar to those for contributions to Chemical Communications except that the work will be of more specialist interest. For Perkin and Dalton Communications inclusion of key experi- mental data is expected. Assessment is carried out by a small nucleus of referees consisting largely of members of the appropriate Editorial Boards. 5.0 Contributions to Mendeleev Communic- ations Mendeleev Communications published jointly by the Royal Society of Chemistry and the Russian Academy of Sciences is a sister publication to Chemical Communications containing preliminary reports of the same type in any area of chemistry.The majority of contributions are from Russian authors. Assessment involves two stages of refereeing. Manuscripts submitted to the Moscow Editorial Office are refereed initially by a Soviet scientist. If found acceptable they are then reviewed by Western scientists chosen by the Royal Society of Chemistry. Manuscripts submitted to the UK Editorial Office undergo this two-stage refereeing process in reverse. 6.0 X-Ray Crystallographic Work 6.1 (A) The majority which contain definitive data on completely refined determinations. (B) A minority which include brief accounts of structures containing feature(s) of unusual interest and where the structure solutions are clear but where (for any of a variety of reasons) the full refinement has not been completed.These are then regarded as preliminary publications at least so far as the X-ray results are concerned. Both types of publication are appropriate for Communic- ations; only those of type (A) should normally appear as full papers. Crystallographic papers are of two types 6.2 It is often appropriate (but not obligatory) for papers of type (A) to contain the information in their titles that an X-ray structure determination has been carried out. Papers of type (B) need not do so if the X-ray determination forms only a minor part. Summaries should always contain this information unless the paper is of type (B) and the structure determination is not a main point of the communication. 6.3 All papers containing crystallographic determinations will be refereed by two referees one a structural chemist.If the editor considers it advisable the paper may also be sent to a crystallographer for comment. Referees will not normally be expected to check values of structural parameters for publication (e.g. bond lengths and angles against atomic co- ordinates; this will be done after publication by CCDC or Bonn) but should still pay attention to the quality of the experimental crystallographic work. However their primary concern should be such new chemistry as is involved in the structure. 6.4 On occasions Communications will contain preliminary accounts [type (B)] of crystal structures of unusual chemical interest. By ‘preliminary’ is meant that the data have not yet been fully refined.Sufficient supplementary data must be provided for the referee to judge whether the ‘not-fully-refined’ structure does indeed prove the desired point and care should be taken by the referees to ensure that the authors do not overstate the case they have-for example by reporting bond lengths to very high degrees of apparent precision when they have poor R-factors. Such papers will always be refereed by a professional crystallographer. Authors must indicate in the paper or the supplementary data the justification for publishing without full refinement and referees should comment on whether the case for publication is convincing. 6.5 In many cases the structure referred to in a Communication will be fully refined. The Communication can then be considered to fulfil the archival function and the structure determination may not require further detailed140 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 refereeing when presented as part of a full paper. In the full paper the author’s purpose will then be served by a simple reference back to the original communication. However if the crystallography is discussed again at any length in the full paper the data should be re-presented to the referees in full and re- published if considered necessary. 6.6 There may be other cases when an author wishes to publish a full paper in which the result of a crystal structure determination is discussed but in which details or extensive discussion are considered unnecessary. The crystallographer may even be omitted as a co-author (for example when the determination is carried out by a commercial company). If the author is able to show the referees that this procedure is appropriate it will be allowed provided that it does not lead to unnecessary fragmentation. However the author must provide as supplementary information sufficient data relating to the crystal structure determination to allow a referee to make sure that the point made is correct and co-ordinates etc. will be deposited with CCDC (or Bonn). The brief published description of the determination should be supplemented by appropriate reference to ‘unpublished work’.

ISSN:0267-9477    

DOI:10.1039/JA9930800137

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL. 8 APPENDIX 141 IUPAC Publications on Nomenclature and Symbolism 1 .O Compilations 1.1 Nomenclature of Organic Chemistry a 550-page hardcover volume published in 1979 available from Pergamon Oxford. Section A Section B Section C Section D Section E Section F Hydrocarbons Fundamental heterocyclic systems Characteristic groups containing carbon hy- drogen oxygen nitrogen halogen sulphur selenium and tellurium Organic compounds containing elements not exclusively those referred to in the title of Section C Stereochemistry General principles for the naming of natural products and related compounds Section H Isotopically modified compounds 1.2 Nomenclature of Inorganic Chemistry a 278-page hardcover volume published in 1990 available from Blackwell Scientific Publications Oxford.Chapter 1 General aims functions and methods Chapter 2 Grammar Chapter 3 Elements atoms and groups Chapter 4 Formulae Chapter 5 Names based on stoichiometry Chapter 6 Neutral molecular compounds Chapter 7 Names for ions substituent groups and radicals and salts Chapter 8 Oxoacids and derived anions Chapter 9 Co-ordination compounds Chapter 10 Boron hydrides and related compounds 1.3 Biochemical Nomenclature and Related Documents a 348-page softcover manual published in 1992 by Portland Press Ltd. for IUBMB and available from the publisher (59 Portland Place London W1N 3AJ UK). The contents are as follows Nomenclature of organic chemistry. Section E Stereo- chemistry (1974) Nomenclature of organic chemistry. Section F Natural products and related compounds (1976) Isotopically modified compounds Recommendations for the presentation of thermodynamic and related data in biology (1985) Citation of bibliographic references in biochemical journals (1971) Nomenclature and symbolism for amino acids and peptides (1983) Abbreviated nomenclature of synthetic polypeptides or polymerized amino acids (197 1) Abbreviations and symbols for the description of the conformation of polypeptide chains (1969) Nomenclature of peptide hormones (1974) Nomenclature of glycoproteins glycopeptides and peptidoglycans (1 985) Nomenclature of initiation elongation and termination factors for translation in eukaryotes (1988) Nomenclature of multiple forms of enzymes (1976) Symbolism and terminology in enzyme kinetics (198 1) Nomenclature for multienzymes (1989) Abbreviations and symbols for nucleic acids poly- nucleotides and their constituents (1970) Abbreviations and symbols for the description of the conformations of polynucleotide chains (1982) Nomenclature for incompletely specified bases in nucleic acid sequences (1984) Carbohydrate nomenclature.Part I (1969) Nomenclature of cyclitols (1973) Numbering of atoms in myo-inositol(l988) Conformational nomenclature for five- and six-membered ring forms of monosaccharides and their derivatives (1980) Nomenclature of unsaturated monosaccharides (1980) Nomenclature of branched-chain monosaccharides (1980) Abbreviated terminology of oligosaccharide chains (1980) Polysaccharide nomenclature (1980) Symbols for specifying the conformation of polysaccharide chains (198 1) Nomenclature of lipids (1976) Nomenclature of steroids (1989) Nomenclature of quinones with isoprenoid side chains (1973) Nomenclature of carotenoids (1 970) and amendments (1974) Nomenclature of tocopherols and related compounds (1981) Nomenclature of vitamin D (1981) Nomenclature of retinoids (1981) Prenol nomenclature (1986) Nomenclature of phosphorus-containing compounds of biochemical importance (1976) Nomenclature and symbols for folic acids and related compounds (1986) Nomenclature for vitamins B-6 and related compounds (1 973) Nomenclature of corrinoids (1973) Nomenclature of tetrapyrroles (1986) 1.4 Compendium of Analytical Nomenclature a 280-page hardcover volume published in 1987 available from Blackwell Scientific Publications Oxford.The contents are as follows Presentation of the Results of Chemical Analysis Solution Thermodynamics (activity coefficients equilibria Recommendations for Terminology to be used with Precision Balances Recommendations for Nomenclature of Thermal Analysis Recommendations for Nomenclature of Titrimetric Analysis Electrochemical Analysis Analytical Separation Processes (precipitation liquid- liquid distribution zone melting and fractional crystallis- ation chromatography ion exchange) Spectrochemical Analysis (radiation sources general atomic emission spectroscopy flame spectroscopy X-ray emission spectroscopy molecular methods) Recommendations for Nomenclature of Mass Spec- trometry Recommendations for Nomenclature of Radiochemical Methods Surface Analysis (including photoelectron spectroscopy) PH)142 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL.8 1.5 Compendium of Macromolecular Nomenclature a 172- page hardcover volume published in 1991 available from Blackwell Scientific Publications Oxford. The contents are as follows Basic Definitions of Terms Relating to Polymers Stereochemical Definitions and Notations Relating to Polymers Definitions of Terms Relating to Individual Macro- molecules their Assemblies and Dilute Polymer Solutions Definitions of Terms Relating to Crystalline Polymers Nomenclature of Regular Single-strand Organic Polymers Nomenclature for Regular Single-strand and Quasi-single- strand Inorganic and Coordination Polymers Source-based Nomenclature for Copolymers A Classification of Linear Single-strand Polymers Use of Abbreviations for Names of Polymeric Substances 1.6 Compendium of Chemical Terminology IUPAC Recommendations a 456-page volume published in 1987 available in hardcover and softcover from Blackwell Scientific Publications Oxford.1.7 Quantities Units and Symbols in Physical Chemistry a 134-page hardcover volume published in 1988 by Black- well Scientific Publications Oxford (new edition to appear 1993). 2.0 Documents not included in the compil- ations 2.1 Boron Compounds Nomenclature of inorganic boron compounds (Pure Appl. Chem. 1972,30,681). Delta Convention Nomenclature for cyclic organic compounds with contiguous formal double bonds (Pure Appl. Chem. 1988,60,1395). Recommendations for the names of elements of atomic number greater than 100 (Pure Appl.Chem. 1979,51,381). Enzyme Nomenclature (1992) published by Academic Press in hardcover and softcover editions. Revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles (Pure Appl. Chem. 1983 55,409). Names for hydrogen atoms ions and groups and for reactions involving them (Pure Appl. Chem. 1988,60,1115). Nomenclature of inorganic chemistry. Part 11. 1. Isotopically modified compounds (Pure Appl. Chem. 1981,53,1887). Treatment of variable valence in organic nomenclature (Pure Appl. Chem. 1984,56,769). Nomenclature of hydrides of nitrogen and derived cations anions and ligands (Pure Appl. Chem. 1982 54 2545). Extension of Rules A-1.1 and A-2.5 concerning numerical terms used in organic chemical nomenclature (Pure Appl.Chem. 1986 58 1693). Nomenclature of Elements and Compounds Elements Enzymes Heterocyclic Compounds Hydrogen Isotopically Modijied Compounds Lambda Convention Nitrogen Hydrides Numerical Terms Polyanions Zeolites Nomenclature of polyanions (Pure Appl. Chem. 1987,59,1529). Chemical nomenclature and formulation of compositions of synthetic and natural zeolites (Pure Appl. Chem. 1979 51 1091). 2.2 Terminology Symbols and Units and Presentation of Results Glossary of terms used in physical organic chemistry (Pure Appl. Chem. 1983,55 1281). Glossary of atmospheric chemistry terms (Pure Appl. Chem. 1990,62,2 167). English-derived abbreviations for experimental techniques in surface science and chemical spectroscopy (Pure Appl.Chem. 1991,63 887). Analytical Recommendations for publication of papers on a new analytical method based on ion exchange or ion-exchange chromato- graphy (Pure Appl. Chem. 1980,52,2555). Recommendations for presentation of data on compleximetric indicators. 1. General (Pure Appl. Chem. 1979,51 1357). Recommendations for publishing manuscripts on ion-selective electrodes (Pure Appl. Chem. 1981,53 1907). Recommendations on use of the term amplification reactions (Pure Appl. Chem. 1982,54,2553). Recommendations for the usage of selective selectivity and related terms in analytical chemistry (Pure Appl. Chem. 1983 55 553). Nomenclature for automated and mechanised analysis (Pure Appl. Chem. 1989,61,1657). Nomenclature for sampling in analytical chemistry (Pure Appl.Chem. 1990,62 1193). Glossary for chemists of terms used in biotechnology (Pure Appl. Chem. 1992,64,143). Selection of terms symbols and units related to microbial processes (Pure Appl. Chem. 1992,64 1047). Physicochemical quantities and units in clinical chemistry with special emphasis on activities and activity coefficients (Pure Appl. Chem. 1984,56,567). Quantities and units in clinical chemistry (Pure Appl. Chem. 1979,51,2451). Quantities and units in clinical chemistry nebulizer and flame properties in flame emission and absorption spectrometry (Pure Appl. Chem. 1986,58,1737). List of quantities in clinical chemistry (Pure Appl. Chem. 1979 51,2481). Proposals for the description and measurement of carry-over effects in clinical chemistry (Pure Appl.Chem. 1991,63 301). Definitions terminology and symbols in colloid and surface chemistry. I (Pure Appl. Chem. 1972 31 577). 11 Hetero- geneous catalysis (Pure Appl. Chem. 1976 46 71). Part 1.14 Light scattering (provisional) (Pure Appl. Chem. 1983 55 93 1). ;Reporting experimental pressure-area data with film balances (Pure Appl. Chem. 1985,57,621). Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity (Pure Appl. Chew. 1985,57,603). Reporting data on adsorption from solution at the solid/ solution interface (Pure Appl. Chem. 1986,58,967). Manual on catalyst characterization (Pure Appl. Chem. 1991 63 1227). General Biotechnology Clinical Colloids and Surface ChemistryJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY FEBRUARY 1993 VOL.8 143 Electrochemistry Nomenclature for transfer phenomena in electrolytic systems (Pure Appl. Chem. 1981,53,1827). Electrode reaction orders transfer coefficients and rate constants-amplification of definitions and recommendations for publication of parameters (Pure Appl. Chem. 1980,52,233). Classification and nomenclature of electroanalytical techniques (Pure Appl. Chem. 1976,45,8 1). Recommendations for sign conventions and plotting of electrochemical data (Pure Appl. Chem. 1976,45 131). Electrochemical nomenclature (Pure Appl. Chem. 1974,37,499). Recommendations on reporting electrode potentials in non-aqueous solvents (Pure Appl. Chem. 1984,56,461). Definition of pH scales standard reference values measurement of pH and related terminology (Pure Appl.Chem. 1985,57,531). Interphases in systems of conducting phases (Pure Appl. Chem. 1986,58,437). The absolute electrode potential an explanatory note (Pure Appl. Chem. 1986,58,955). Electrochemical corrosion nomenclature (Pure Appl. Chem. 1989,61 19). Terminology in semiconductor electrochemistry and photo- electrochemical energy conversion (Pure Appl. Chem. 199 1,63 569). Nomenclature symbols definitions and measurements for electrified interfaces in aqueous dispersions of solids (Pure Appl. Chem. 1991,63,895). Symbolism and terminology in chemical kinetics (provisional) (Pure Appl. Chem. 1981,53,753). Recommended standards for reporting photochemical data (Pure Appl. Chem. 1984,56,939). Glossary of terms used in photochemistry (Pure Appl.Chem. 1988,60,1055). Expression of results in quantum chemistry (Pure Appl. Chem. 1978,50 75). Reactions Nomenclature for organic chemical transformations (Pure Appl. Chem. 1989,61,725). System for symbolic representation of reaction mechanisms (Pure Appl. Chem. 1989,61,23). Detailed linear representation of reaction mechanisms (Pure Appl. Chem. 1989,61,57). Rheological Properties Selected definitions terminology and symbols for rheological properties (Pure Appl. Chem. 1979,51 1215). Kinetics Photochemistry Quan tum Chemistry Spectroscopy Recommendations for publication of papers on methods of molecular absorption spectrophotometry in solution (Pure Appl. Chem. 1978,50 237). Recommendations for the presentation of infrared absorption spectra in data collections. A Condensed phases (Pure Appl.Chem. 1978,50,23 1). Definition and symbolism of molecular force constants (Pure Appl. Chem. 1978,50 1709). Nomenclature and conventions for reporting Mossbauer spectroscopic data (Pure Appl. Chem. 1976,45,211). Recommendations for the presentation of NMR data for publication in chemical journals. A Proton spectra (Pure Appl. Chem. 1972,29,625). B Spectra from nuclei other than protons (Pure Appl. Chem. 1976,45,217). Presentation of Raman spectra in data collections (Pure Appl. Chem. 1981,53 1879). Names symbols definitions and units of quantities in optical spectroscopy (Pure Appl. Chem. 1985,57,105). A descriptive classification of the electron spectroscopies (Pure Appl. Chem. 1987,59,1343). Presentation of molecular parameter values for IR and Raman intensity (Pure Appl.Chem. 1988,60 1385). Recommendations for EPR/ESR nomenclature and conven- tions for presenting experimental data in publications (Pure Appl. Chem. 1989,61,2195). Nomenclature symbols units and their usage in spectro- chemical analysis. VII. Molecular absorption spectroscopy UV and visible (Pure Appl. Chem. 1988 60 1449); VIII. Nomenclature system for X-ray spectroscopy (Pure Appl. Chem. 1991,63,735); X. Preparation of materials for analytical atomic spectroscopy (Pure Appl. Chem. 1988 60 1461); XII. Terms related to electrothermal atomization (Pure Appl. Chem. 1992 64 253); XIII. Terms related to chemical vapour generation (Pure Appl. Chem. 1992,64,261). Recommendations for nomenclature and symbolism for mass spectroscopy (Pure Appl. Chem. 1991,63 1541). A guide to procedures for the publication of thermodynamic data (Pure Appl. Chem. 1972,39,395). Assignment and presentation of uncertainties of the numerical results of thermodynamic measurements (Pure Appl. Chem. 198 1,53 1805). Notation for states and processes; significance of the word ‘standard’ in chemical thermodynamics and remarks on commonly tabulated forms of thermodynamic functions (Pure Appl. Chem. 1982,54 1239). Thermodynamics

ISSN:0267-9477    

DOI:10.1039/JA9930800141

出版商:RSC    

年代:1993

数据来源: RSC