JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, MARCH 1992, VOL. 7 11N

Sir Alan Walsh-The Scientist and the Man P. L. Larkins CSIRO, Division of Materials Science and Technology, Locked Bag 33, Clayton, Victoria 31 68, Australia

I would like to start by saying that I am delighted to have been given the opportunity to participate in this pre- sentation of the inaugural CSI-Award to Sir Alan Walsh. I believe that it would be difficult to find a more fitting recipient of this award and I congratu- late those who were responsible for this decision.

I would like to present to you, briefly, my view of Alan's work and its importance, and also to give some personal views of Alan derived from working with him for nearly 10 years prior to his retirement in 1976 and in a less formal association since then.

Various details of Alan's early years have been recorded in the l i terat~rel-~ so I will give only a very brief sum- mary. Alan was born in Lancashire in England in 1916 and was one of a family of four children; one sister and two brothers. He was educated in England at the Danven Grammar School and then at Manchester University where he studied physics, specializing in X-ray crystallography. He commenced his scientific career in 1939 with the British Non-Ferrous Metals Association working on spec- trochemical methods of analysis, and in the short period up to the end of the war he had become a recognized ex- pert in this field, particularly in rela- tion to source units for arc and spark spectrograph y .

In 1946 Alan joined the CSIR (later CSIRO) in Australia as the first mem- ber of the Spectroscopy Group which was being formed in the Chemical Physics Section of the division of Industrial Chemistry. He was appointed to carry out research in

optical spectroscopy, especially infra- red (IR), and he arrived in Australia in April 1947 to commence work in this area. By 195 1 he had made a substan- tial contribution to instrumentation in this field by inventing and patenting a double-pass (multiple) mono- chromatol"' which gave increased reso- lution and decreased stray light. A commercial version of this instrument was produced soon after by Perkin- Elmer under licence to CSIRO and production continued for many years. Thus even prior to his work on atomic absorption spectroscopy Alan had established himself as gin ex- tremely capable and inventive spec- troscopist.

Although Alan continued his work and interest in IR spectroscopy until about 1958, the invention of atomic absorption spectroscopy began with a thought which occurred to him one Sunday in March 1952 while he was working in his garden. In this regard he is in company with one of the previous great physicists, Sir Isaac Newton, of whom it is reported that he came to a realization of the laws of gravitation while watching apples falling from trees. Perhaps there is a moral in this; that those among us who aspire to greater things should spend more time gardening. In Alan's case the realiza- tion that the measurement of atomic absorption constituted a possible new method of analysis must have made him quite excited as he then went to the telephone to discuss his new in- sight with one of hiss colleagues.

His initial attempt at measuring the absorption by atoms in a flame was successful but the more difficult task of

convincing the rest of the world of the value of the technique was only just beginning. In fact, when he then de- monstrated his results to some of his colleagues their response was 'Well, so hat?'.^ Alan's initial papers on this topic are quite remarkable, not only because the details of the instrumenta- tion which he proposed are essentially those which are still in use today, but also because in those early papers he proposed many of the other variations and developments of the technique which have since been investigated either at CSIRO or by others. Some examples of these techniques are ca- thodic sputtering for sample atomiza- tion, resonance detectors and selective modulation. It is interesting to note that in his first papee Alan even referred to the possible use of a (vacuum) furnace for sample atomiza- tion, however no work on furnaces was carried out at CSIRO.

In regard to the basic technique, Alan has written' that he 'had the great good fortune to select flames for atom- ization and hollow cathode lamps for light sources'. In addition he had used an a.c. detection system to avoid prob- lems from flame emission. I believe that all these choices were not the result of good luck but arose from a thorough understanding of the various possible light sources and atomization and detection systems. This under- standing had been gained during his earlier work on arc and spark emission and on IR and Raman spectroscopy. Perhaps the only piece of good fortune was the fact that he had the opportu- nity to carry out extensive work in both these fields and had a keen

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12N JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, MARCH 1992, VOL. 7

interest in, and understanding of, the instrumentation associated with these techniques.

Closing the gap between the initial thought and the final product of com- mercial standard required extensive work on the part of Alan and the group that he gathered to work on the pro- ject. Development of each of the main components of the atomic absorption instrument required almost a separate research project for each component and the work involved could be dis- cussed at length, but I will indicate the size of the project by reference to the work on light sources. The truly crea- tive part of this work was the initial realization that the problem of the narrow width of flame absorption lines could be overcome by the use of a light source with an even narrower emission line. This represented a substantial departure from existing absorption techniques which used continuum light sources combined with a mono- chromator to provide the required spectral bandwidth.

In his Raman spectroscopy work Alan had worked with microwave lamps, and his initial experiments with atomic absorption had involved lab- oratory discharge lamps. While either of these types of lamps could have been chosen for further development he realized that neither would be capable of providing for the elemental coverage inherent in the technique itself. Instead he chose to base further work on the hollow cathode lamp. This was not a trivial decision since, at that time, hollow cathode lamps were generally made by the scientists using them and had only short lifetimes. The aim of the work at CSIRO was to develop these lamps in a sealed form with a reasonable lifetime and to be able to make them for all the elements accessible to the atomic absorption technique. This aim was eventually achieved and the wisdom of the initial choice of the hollow cathode is demon- strated by the fact that they are still the main type of light source used in atomic absorption spectroscopy.

Having developed the sealed hollow cathode lamp, work in this area was not abandoned. In association with Jack Sullivan,’ Alan proceeded to de- velop a modified form of this lamp, which they called a high-intensity (or boosted-output) hollow cathode lamp. This modified lamp had the advan- tages of higher intensity combined with narrow linewidths but in this work they were too far ahead of their time. Some of these lamps were pro- duced commercially for a few years in the late 1970s but then interest waned. However, developments in atomic fluorescence and the introduction of the carbon furnace revived the need

for more intense light sources and a more highly developed version of this lamp is now in production by the Australian firm, Photron Pty. Ltd., and is meeting with rapidly growing commercial success.

I first became aware of AAS in the early 1960s and I was very impressed. This technique did far inorganic ana- lysis what chromatographic methods, and gas chromatography in particular, had done for organic analysis. Here was a technique which could be used for an enormous range of sample types with little or no pre-treatment other than that required to bring the sample into solution. This provided an enor- mous increase in productivity, as some analyses which required a day or more using previous techniques could now be carried out in less than a minute.

Apart from the benefit to analytical chemists worldwide which came from the development and promotion of AAS, there were, and continue to be, real and substantial benefits to Australia which result from this work having been carried out within CSIRO. A cost benefit analysis carried out in 1 9698 conservatively estimated the value to the country to that date to be $20-$23 million. An on-going be- nefit is the fact that this work resulted in the establishment within Australia of two firms which now rank second and third in the world in production of atomic absorption spectrometers. Al- though there were some small instru- ment firms operating previously, the manufacture of AAS instruments represented the real birth of the scien- tific instrument industry in Australia.

The benefits from AAS, however, are not all counted in economic terms. Very early in the development of atomic absorption a 7 year old boy had been undergoing treatment in a Syd- ney (Australia) hospital for extensive bums. During the course of his treat- ment he developed convulsions and seemed likely to die. An early atomic absorption unit was used to measure magnesium in his blood and this was found to be very low. Treatment with magnesium salts stopped the convul- sions and he recovered ~ompletely.~ Prior to the introduction of atomic absorption the determination of mag- nesium in blood was very difficult.

Moving now to ,41an himself, I believe that perhaps the most impor- tant personal characteristic which he brought to his work was enthusiqsm. As those working in (science will know, the best scientists inre not detached observers, but rather they have a keen, almost passionate, involvement in their work and the development of their ideas, and promote them enthusi- astically to their colleagues.

In addition to enthusiasm, of course,

one has to have something to be enthusiastic about. In Alan’s case this was not a, problem as he often came into the laboratory with new ideas to discuss or new suggestions to over- come problems in current work. In fact there was one memorable occasion when some work was being carried out on a sputtering-fluorescence tech- nique. Alan made a suggestion which it was estimated would improve the re- sults by a factor of about two. He returned to his office but came back a while later with another suggestion to give another factor of two improve- ment. By lunchtime it was estimated that he had been back 15 times and simple mathematics indicated that the total improvement resulting from his suggestions should be 2 to the power of 15, i.e., about 32000. Actually, many of the ideas were useful but the im- provements never reached the esti- mated figure. Not all of Alan’s ideas fell on receptive ears, however. Alan has occasionally related a story con- cerning a laboratory assistant who worked for him early in the AAS project. Some time after this person had left CSIRO, Alan was looking through her note book and on one page found the cryptic comment ‘Boss sug- gests try. . . ’, followed by some results. On the next page was the equally cryptic comment ‘Didn’t work‘. Some pages on was another note, ‘Boss sug- gests try. . . ’, more results and then ‘Didn’t work either’.

Of Alan’s various ideas for improve- ment or modification of atomic ab- sorption or related methods, none have met with the success of the original idea, but this is not surprising. The basic simplicity and broad range of application of AAS more than satisfied most analytical requirements for many years. Although some of his ideas were aimed at problems which are now either much reduced in im- portance or no longer exist, others, such as sputtering-atomization and boosted hollow cathode lamps (as mentioned earlier) are now having a renaissance and may well see further development in the future.

Another characteristic which stood out in Alan’s approach to his work was the desire to keep it simple. This simplicity was obvious in most of the equipment depicted in the early papers on the subject, and also in develop- ments in areas such as selective modu- lation. This latter technique effectively put the functions of both the light source and monochromator within the lamp envelope. Unfortunately, simpli- city and versatility do not often go together and generally users have opted for versatility with its related complexity.

Other characteristics which made it

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JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, MARCH 1992, VOL. 7 13N

a pleasure to work with Alan were his tolerance and his sense of humour. In my early days at CSIRO as a relatively young scientist, there were times when I made suggestions or offered opinions which were based on inadequate knowledge. I was never ridiculed but mostly had my ideas discussed and from this I learnt much and with little pain. Alan has many humorous stories to tell of the early days of AAS and some of these have appeared in his written accounts of those times.s

During his career Alan has received many honours and awards. I will not try to list them all but among the more prestigious are: being made a Knight Bachelor in 1977, and election to Fellowship of the Royal Society and Foreign membership of the Royal Aca- demy of Sciences, Stockholm. Among his many medals are the Royal Medal of the Royal Society, the Analytical Division of The Royal Society of

Chemistry Robert Boyle Medal in An- alytical Chemistry, the Talanta Gold Medal and the Maurice Hastler Award of the Society for Applied Spectro- scopy (USA). All the honours and awards which he has received over the years have not altered his generous and friendly nature. In fact, he recently agreed to be the subject of a young boy’s school project and readily made the time available to be interviewed. As the young lad noted in the introduc- tion to his report, despite ‘his achieve- ments.. . he still doesn’t get big headed’.

In finishing I would like to add a final thought. We are, of course, here to honour Sir Alan Walsh, but it is often said that beliind every great man is a great woman and I believe that this is true also for Alan. It would be difficult to find a warmer, friendlier lady than Lady Walsh, Audrey to all her many friends, and I have no doubt

that she has been an enormous help to Alan throughout his career. Perhaps this is the area of his life in which he had great good fortune.

References Walsh, A., Chzmica, 1980, 34, 427. Willis, J. B., Hist. Rec. Aust. Sc., 1988, 7 , 153. Annual Report, CSIRO Division of Chemical Physics, 1976177. Walsh, A., Aust. Phys., 1990, 27, 164. Walsh, A., Anal. Chem., 1974, 46, 698A. Walsh, A., Spectrochim. Acta, 1955, 7 , 108. Sullivan, J. V., and Walsh, A., Spectro- chim. Acta, 1965, 21, 721. Brown, A. W., CSIRO Industrial Re- search News, No. 76, July 1969. Willis, J. B., Spectrochim. Acta, Part B, 1980, 35, 653.

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