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Early developments in atomic-absorption spectrochemical analysis
Spectrochimica Acta Part B 54 Ž1999. 1967]1969
Early developments in atomic-absorption spectrochemical analysis q D.J. David 208 Yurunga Dri¨ e, North Nowra, NSW 2541, Australia Received 15 April 1999; accepted 22 August 1999
Keywords: CSIRO; Atomic absorption; Rukuhia Soil Research Station
1. Introduction I first met Alan Walsh in 1948 in Melbourne, we being fellow workers for the Council for Scientific and Industrial Research there, he in the Chemical Physics Section of the Division of Industrial Chemistry, I in the Building Research Section. I moved to Adelaide in 1950, then to Canberra in 1953 to work in the Division of Plant Industry of the newly formed Commonwealth Scientific and Industrial Research Organisation ŽCSIRO. on the application of spectrochemical methods to agricultural analysis. This meant that our pursuits became similar. He was later Ž1961.
q
This paper was published in the Special Issue in memory of Sir Alan Walsh, the premier pioneer of atomic absorption spectrometry.
appointed Assistant Chief of the CSIRO, Division of Chemical Physics, formed in 1958.
2. Origins of first investigations of atomic absorption To exploit his outstanding concept w1x of the use of atomic absorption rather than atomic or molecular emission in spectrochemical analysis, Walsh embarked upon publicising it among practising analysts and devised simple equipment vital to its efficient operation w2x. Eric Allan ŽNew Zealand. and I agreed in a discussion with him, after a conference in Melbourne in the mid-1950s, to look at its application to agricultural analysis. Eric Allan said he would look at manganese and iron sensitivity w3x, as well as the determination of magnesium w4x, while I undertook first to investi-
0584-8547r99r$ - see front matter Q 1999 Published by Elsevier Science B.V. All rights reserved. PII: S 0 5 8 4 - 8 5 4 7 Ž 9 9 . 0 0 1 2 1 - 4
1968
D.J. Da¨ id r Spectrochimica Acta Part B: Atomic Spectroscopy 54 (1999) 1967]1969
gate the determination of some trace elements Žwhich turned out to be interference-free . w5x, then to examine the determination of calcium w6x knowing that, in flame-emission analysis, it was subject to other sample components interfering with the production of free calcium atomic vapour in the flame. Interferences depressing the formation of atomic vapour of calcium could be overcome, it was found, by the addition of excesses of empirically chosen elements to both sample and calibration solutions, while an enhancement could be overcome by the addition of an excess of the element causing it to both sample and calibration solutions. In cases of extremely severe interference Žsuch as in the determination of strontium in plant material. it was found necessary to remove the interfering components using ion-exchange resins. Studies were also carried out into the use of the well-known Analyte Addition Technique of analysis Žearlier called the Addition Method. which compensates for interference effects, e.g. David w8x.
3. Eric Allan and his work Eric, who worked at the Rukuhia Soil Research Station, Hamilton, New Zealand, studied the relative absorption sensitivities of different lines of manganese, iron, copper, cobalt and nickel, and showed how to determine the first three of these elements in plant material after ashing w3,7,9x. He made a number of other early contributions to spectrochemical analysis by flame atomic absorption, including the determination of magnesium in plant ash and other materials w4x. He developed the use of the broad-spectrum complexing agent, ammonium 1-pyrrolidinecarbodithioate, to extract heavy metals from aqueous solution and to concentrate them into an organic solvent such as 2-methyl-4-pentanone which could be sprayed into a pre-mixed flame w10,11x. He also showed that the increase in absorption obtained when spraying solutions of metals in organic solvents in place of water could be accounted for almost quantitatively by the greater rate at which the solutions reached the flame. This work corrected a number of erroneous ideas that had been put
forward to account for the effect of organic solvents on intensity of absorption.
4. Instrumentation employed I built two instruments in my laboratory. The first w5x employed a Hilger Medium Quartz spectrograph with Lundegardh spray bulbs and air]acetylene burner assembly giving approximately a 2.0-cm flame-pass. An improvised exit slit and photomultiplier assembly, moveable along the focal plane of the spectrograph, was mounted in place of the plate-holder. Later, the cumbersome Lundergardh system was replaced with an E.E.L. ŽEvans Electroselenium Ltd. nebulising system on which was mounted a stainless steel tube crimped at one end to give a horizontally elongated flame, providing a 2.7-cm path-length of the hollow-cathode beam through the flame. This was used for the determination of major elements in plants and also of trace concentrations of elements of high sensitivity. The modulated electronic system used, details later published w2x, was generously provided by Alan Walsh on a visit I made to Alan and his colleagues’ laboratory early in 1958. Apart from the agricultural studies already mentioned, research was also carried out into the use of this equipment in the determination of exchangeable cations in soils w12x. The second instrument w13x, having a 10-cm beam path-length through the flame and a scaleexpansion system, was used for the general determination of trace elements. On another visit to Alan Walsh’s laboratory, I borrowed an apparently surplus silicone oil diffusion pump which I took back to my laboratory and, with the aid of a mechanical backing pump I already had, constructed a high-vacuum line. I used this to recharge failed hollow-cathode lamps with spectrally-pure argon or neon. However, on realising the possibility of volatilising molybdic oxide from sample particles in an air]acetylene flame, as a result of earlier arc-emission work w14x, I used the high-vacuum line also to fashion a molybdenum hollow-cathode lamp Ždescribed in David w13x.. This resulted in the finding w8x that a reducing air]acetylene flame could generate from
D.J. Da¨ id r Spectrochimica Acta Part B: Atomic Spectroscopy 54 (1999) 1967]1969
sample solutions, and sustain, analytically-useful quantities of atomic vapour of molybdenum at a temperature some 28008C below the boiling point of metallic molybdenum. That molybdenum might be vaporised as molybdic oxide from sample particles containing it in an air]acetylene flame arose from the observation w14x that precision in the determination of molybdenum by arc-emission methods was very much higher than that observed in the determination of other elements of supposedly equally low volatility Že.g. manganese.. That is, it must enter the arc stream early in the arcing period when volatile components of low ionisation potential produce a steadier and less erratic arc than occurs towards the end of the arcing period when the more refractory components of the sample are being vaporised. Molybdic oxide sublimes spontaneously at 7958C w15x. Alan Walsh facilitated the testing of the flame atomic absorption implications of these notions by generously providing me with the means of making a molybdenum hollow-cathode lamp.
Acknowledgements I thank Dr J.B. Willis for providing details of the late J.E. Allan’s contributions to early development of atomic absorption analysis. References w1x A. Walsh, The application of atomic absorption spectra to chemical analysis, Spectrochim. Acta 7 Ž1955. 108]117; erratum ibid, p. 252.
1969
w2x G.F. Box, A. Walsh, A simple atomic absorption spectrophotometer, Spectrochim. Acta 16 Ž1960. 255]258. w3x J.E. Allan, The determination of iron and manganese by atomic absorption, Spectrochim. Acta 15 Ž1959. 800]806. w4x J.E. Allan, Atomic absorption spectrophotometry with particular reference to the determination of magnesium, Analyst 83 Ž1958. 466]471. w5x D.J. David, The determination of zinc and other elements in plants by atomic absorption spectroscopy, Analyst 83 Ž1958. 655]661. w6x D.J. David, The determination of calcium in plant material by atomic absorption spectrophotometry, Analyst 84 Ž1959. 536]545. w7x J.E. Allan, The determination of copper by atomic absorption spectrophotometry, Spectrochim. Acta 17 Ž1961. 459]466. w8x D.J. David, Atomic absorption spectrophotometric determination of molybdenum and strontium, Nature 187 Ž1960. 1109. w9x J.E. Allan, The determination of nickel and cobalt by atomic absorption, Nature 187 Ž1960. 1110. w10x J.E. Allan, The use of organic solvents in atomic absorption spectrophotometry, Spectrochim. Acta 17 Ž1961. 467]473. w11x J.E. Allan, The determination of zinc in agricultural materials by atomic absorption spectroscopy, Analyst 96 Ž1961. 530]534. w12x D.J. David, The determination of exchangeable sodium, potassium, calcium and magnesium in soils by atomic absorption spectrophotometry, Analyst 85 Ž1960. 495]503. w13x D.J. David, The determination of molybdenum by atomic absorption spectrophotometry, Analyst 86 Ž1961. 730]740. w14x D.J. David, The Spectrochemical Determination of Some Trace Elements in Plant Ash, M.Sc. dissertation, vol. 1, University of Western Australia, Nedlands, Western Australia, July 1951. w15x Handbook of Chemistry and Physics, Chemical Rubber Publishing Co., 1949.
Early developments in atomic-absorption spectrochemical analysis q D.J. David 208 Yurunga Dri¨ e, North Nowra, NSW 2541, Australia Received 15 April 1999; accepted 22 August 1999
Keywords: CSIRO; Atomic absorption; Rukuhia Soil Research Station
1. Introduction I first met Alan Walsh in 1948 in Melbourne, we being fellow workers for the Council for Scientific and Industrial Research there, he in the Chemical Physics Section of the Division of Industrial Chemistry, I in the Building Research Section. I moved to Adelaide in 1950, then to Canberra in 1953 to work in the Division of Plant Industry of the newly formed Commonwealth Scientific and Industrial Research Organisation ŽCSIRO. on the application of spectrochemical methods to agricultural analysis. This meant that our pursuits became similar. He was later Ž1961.
q
This paper was published in the Special Issue in memory of Sir Alan Walsh, the premier pioneer of atomic absorption spectrometry.
appointed Assistant Chief of the CSIRO, Division of Chemical Physics, formed in 1958.
2. Origins of first investigations of atomic absorption To exploit his outstanding concept w1x of the use of atomic absorption rather than atomic or molecular emission in spectrochemical analysis, Walsh embarked upon publicising it among practising analysts and devised simple equipment vital to its efficient operation w2x. Eric Allan ŽNew Zealand. and I agreed in a discussion with him, after a conference in Melbourne in the mid-1950s, to look at its application to agricultural analysis. Eric Allan said he would look at manganese and iron sensitivity w3x, as well as the determination of magnesium w4x, while I undertook first to investi-
0584-8547r99r$ - see front matter Q 1999 Published by Elsevier Science B.V. All rights reserved. PII: S 0 5 8 4 - 8 5 4 7 Ž 9 9 . 0 0 1 2 1 - 4
1968
D.J. Da¨ id r Spectrochimica Acta Part B: Atomic Spectroscopy 54 (1999) 1967]1969
gate the determination of some trace elements Žwhich turned out to be interference-free . w5x, then to examine the determination of calcium w6x knowing that, in flame-emission analysis, it was subject to other sample components interfering with the production of free calcium atomic vapour in the flame. Interferences depressing the formation of atomic vapour of calcium could be overcome, it was found, by the addition of excesses of empirically chosen elements to both sample and calibration solutions, while an enhancement could be overcome by the addition of an excess of the element causing it to both sample and calibration solutions. In cases of extremely severe interference Žsuch as in the determination of strontium in plant material. it was found necessary to remove the interfering components using ion-exchange resins. Studies were also carried out into the use of the well-known Analyte Addition Technique of analysis Žearlier called the Addition Method. which compensates for interference effects, e.g. David w8x.
3. Eric Allan and his work Eric, who worked at the Rukuhia Soil Research Station, Hamilton, New Zealand, studied the relative absorption sensitivities of different lines of manganese, iron, copper, cobalt and nickel, and showed how to determine the first three of these elements in plant material after ashing w3,7,9x. He made a number of other early contributions to spectrochemical analysis by flame atomic absorption, including the determination of magnesium in plant ash and other materials w4x. He developed the use of the broad-spectrum complexing agent, ammonium 1-pyrrolidinecarbodithioate, to extract heavy metals from aqueous solution and to concentrate them into an organic solvent such as 2-methyl-4-pentanone which could be sprayed into a pre-mixed flame w10,11x. He also showed that the increase in absorption obtained when spraying solutions of metals in organic solvents in place of water could be accounted for almost quantitatively by the greater rate at which the solutions reached the flame. This work corrected a number of erroneous ideas that had been put
forward to account for the effect of organic solvents on intensity of absorption.
4. Instrumentation employed I built two instruments in my laboratory. The first w5x employed a Hilger Medium Quartz spectrograph with Lundegardh spray bulbs and air]acetylene burner assembly giving approximately a 2.0-cm flame-pass. An improvised exit slit and photomultiplier assembly, moveable along the focal plane of the spectrograph, was mounted in place of the plate-holder. Later, the cumbersome Lundergardh system was replaced with an E.E.L. ŽEvans Electroselenium Ltd. nebulising system on which was mounted a stainless steel tube crimped at one end to give a horizontally elongated flame, providing a 2.7-cm path-length of the hollow-cathode beam through the flame. This was used for the determination of major elements in plants and also of trace concentrations of elements of high sensitivity. The modulated electronic system used, details later published w2x, was generously provided by Alan Walsh on a visit I made to Alan and his colleagues’ laboratory early in 1958. Apart from the agricultural studies already mentioned, research was also carried out into the use of this equipment in the determination of exchangeable cations in soils w12x. The second instrument w13x, having a 10-cm beam path-length through the flame and a scaleexpansion system, was used for the general determination of trace elements. On another visit to Alan Walsh’s laboratory, I borrowed an apparently surplus silicone oil diffusion pump which I took back to my laboratory and, with the aid of a mechanical backing pump I already had, constructed a high-vacuum line. I used this to recharge failed hollow-cathode lamps with spectrally-pure argon or neon. However, on realising the possibility of volatilising molybdic oxide from sample particles in an air]acetylene flame, as a result of earlier arc-emission work w14x, I used the high-vacuum line also to fashion a molybdenum hollow-cathode lamp Ždescribed in David w13x.. This resulted in the finding w8x that a reducing air]acetylene flame could generate from
D.J. Da¨ id r Spectrochimica Acta Part B: Atomic Spectroscopy 54 (1999) 1967]1969
sample solutions, and sustain, analytically-useful quantities of atomic vapour of molybdenum at a temperature some 28008C below the boiling point of metallic molybdenum. That molybdenum might be vaporised as molybdic oxide from sample particles containing it in an air]acetylene flame arose from the observation w14x that precision in the determination of molybdenum by arc-emission methods was very much higher than that observed in the determination of other elements of supposedly equally low volatility Že.g. manganese.. That is, it must enter the arc stream early in the arcing period when volatile components of low ionisation potential produce a steadier and less erratic arc than occurs towards the end of the arcing period when the more refractory components of the sample are being vaporised. Molybdic oxide sublimes spontaneously at 7958C w15x. Alan Walsh facilitated the testing of the flame atomic absorption implications of these notions by generously providing me with the means of making a molybdenum hollow-cathode lamp.
Acknowledgements I thank Dr J.B. Willis for providing details of the late J.E. Allan’s contributions to early development of atomic absorption analysis. References w1x A. Walsh, The application of atomic absorption spectra to chemical analysis, Spectrochim. Acta 7 Ž1955. 108]117; erratum ibid, p. 252.
1969
w2x G.F. Box, A. Walsh, A simple atomic absorption spectrophotometer, Spectrochim. Acta 16 Ž1960. 255]258. w3x J.E. Allan, The determination of iron and manganese by atomic absorption, Spectrochim. Acta 15 Ž1959. 800]806. w4x J.E. Allan, Atomic absorption spectrophotometry with particular reference to the determination of magnesium, Analyst 83 Ž1958. 466]471. w5x D.J. David, The determination of zinc and other elements in plants by atomic absorption spectroscopy, Analyst 83 Ž1958. 655]661. w6x D.J. David, The determination of calcium in plant material by atomic absorption spectrophotometry, Analyst 84 Ž1959. 536]545. w7x J.E. Allan, The determination of copper by atomic absorption spectrophotometry, Spectrochim. Acta 17 Ž1961. 459]466. w8x D.J. David, Atomic absorption spectrophotometric determination of molybdenum and strontium, Nature 187 Ž1960. 1109. w9x J.E. Allan, The determination of nickel and cobalt by atomic absorption, Nature 187 Ž1960. 1110. w10x J.E. Allan, The use of organic solvents in atomic absorption spectrophotometry, Spectrochim. Acta 17 Ž1961. 467]473. w11x J.E. Allan, The determination of zinc in agricultural materials by atomic absorption spectroscopy, Analyst 96 Ž1961. 530]534. w12x D.J. David, The determination of exchangeable sodium, potassium, calcium and magnesium in soils by atomic absorption spectrophotometry, Analyst 85 Ž1960. 495]503. w13x D.J. David, The determination of molybdenum by atomic absorption spectrophotometry, Analyst 86 Ž1961. 730]740. w14x D.J. David, The Spectrochemical Determination of Some Trace Elements in Plant Ash, M.Sc. dissertation, vol. 1, University of Western Australia, Nedlands, Western Australia, July 1951. w15x Handbook of Chemistry and Physics, Chemical Rubber Publishing Co., 1949.