Alan Walsh

English physicist and chemist

• Born: December 19, 1916
• Birthplace: Hoddlesden, Lancashire, England
• Died: August 3, 1998
• Place of death: Melbourne, Australia

Walsh invented atomic absorption spectroscopy to identify the presence of chemical elements in samples and determine their concentration. This method was quick, easy, accurate, highly sensitive, and free from interference. It revolutionized quantitative analysis and was widely applied to a variety of diverse areas.

Primary fields: Chemistry; physics

Primary invention: Atomic absorption spectroscopy

Early Life

Alan Walsh was born in England, approximately twenty miles north of Manchester, in Hoddlesden, a small borough of Darwen, Lancashire. His father, Thomas Haworth Walsh, managed a small family cotton mill in Hoddlesden. His mother, Betsy Alice Walsh (née Robinson), was a very warm and gracious woman. At ten years of age, Walsh attended the local grammar school in Darwen. He passed the Northern Universities Matriculation Examination in 1933. At sixteen, eyestrain persuaded Walsh to concentrate on mathematics, chemistry, and physics. He completed his Higher School Certificate Examination in 1935, and his physical science prowess won him an honors course in physics at the University of Manchester.

Walsh flourished at the University of Manchester. While there, he attended a lecture by Sir Lawrence Bragg, who had won the Nobel Prize in Physics in 1915 for his work on X-ray crystal structure analysis. Bragg’s lecture captivated and energized the young Walsh and influenced him to pursue a research career. Walsh graduated from Manchester in 1938 and was awarded a research scholarship to pursue postgraduate research in physics. He initially worked on the structure of mineral crystals but later switched to crystal structures of beta-carotene, a chemical from plants that serves as a precursor to vitamin A. He only spent one year at the Manchester College of Technology, since the onset of World War II compelled Walsh to refocus his efforts. During the war, Walsh worked for the British Non-Ferrous Metals Research Association (BNF). Walsh continued to work on the beta-carotene project in his spare time after he moved to the BNF.

While at the BNF, Walsh analyzed metals from German war planes that had been shot down. He devised several methods for the rapid and accurate identification of aluminum, copper, and zinc alloys. In 1944, Walsh completed his work on beta-carotene and was awarded a master of science degree in 1944 for a thesis entitled “An X-ray Examination of Beta-carotene.”

Life’s Work

In January, 1945, Walsh became the chief spectroscopist at the BNF and oversaw all spectrographic research. He developed a technique for detecting impurities in uranium metal. In May, 1946, Walsh immigrated to Australia to work in the Chemical Physics Section of the Division of Industrial Chemistry at the Council for Scientific and Industrial Research (CSIR), which became the Commonwealth Scientific and Industrial Research Organization (CSIRO) in 1949. At CSIR/CSIRO, Walsh experienced a near scientific utopia. Instrumentation in the CSIRO laboratories was state of the art, and bureaucratic red tape was kept to a minimum. Investigators were given tremendous freedom to work on their own, and the atmosphere was highly collegial and collaborative. His first project involved installing the new Perkin-Elmer Model 12B spectrometer. He noted that this machine could not resolve the spectra of larger molecules. Therefore, he designed the “double-pass monochromator” to improve the resolution of the machine, which he patented in 1950.

In March, 1952, Walsh experienced a flash of insight while working in his garden. Chemical analyses at this time were conducted in one of two ways. The first method placed the material under analysis between two discharging electrodes. The light emitted by the material under these conditions provided the means of identifying the elements that composed the material and, by comparison to standard samples, the amount of the elements present in the material as well. A second procedure examined the light given off when a solution of the material was sprayed into a flame. Both procedures were fraught with problems that limited their application. Walsh realized that an atomic vapor absorbs light energy at wavelengths peculiar to its chemical composition. The problem was that a vaporized compound emitted light at the same wavelengths at which it absorbed. However, by detecting the decrease in light emission at the most robust wavelength, an investigator could not only identify the presence of a particular element but also determine the amount of that element present in the sample. The other wavelengths of light emitted by the vaporized material could be eliminated by using amplifiers that were tuned to only the desired wavelength. Walsh went to work the next day and performed a trial experiment with sodium atoms and succeeded. This and other follow-up experiments formed the basis of atomic absorption spectroscopy.

After solving problems and substantially improving his new technique, Walsh filed his final patent specification on October 21, 1954, and published his new technique in 1955 in the journal Spectrochimica Acta. The reaction to his work by the scientific community was subdued, since many saw it as a scientific curiosity rather than a practical analytical method. However, an Australian company, Hilger and Watts, entered into an exclusive license agreement with CSIRO to make a commercial atomic absorption machine. Unfortunately, they were unable to produce one that was viable.

In 1958, Walsh was elected a fellow of the Australian Academy of Science. That same year, he was invited to give his first presentation on American soil about atomic absorption spectroscopy. At the Louisiana State University Symposium on Analytical Chemistry, Walsh met spectroscopist James W. Robinson from Esso Research, Baton Rouge. Robinson’s excitement about atomic absorption spectroscopy inspired him to collaborate with Walsh. In 1962, Robinson and his colleagues demonstrated that atomic absorption spectroscopy had widespread application in the analysis of most metals and metalloids. This work demonstrated the industrial uses of atomic absorption spectroscopy and the need for commercially produced machines that could effectively use it. Walsh also met a representative from the scientific instrumentation manufacturer Perkin-Elmer. This interaction motivated Perkin-Elmer to form a research group dedicated to developing an atomic absorption instrument in 1960. In 1963, the company shipped its first atomic absorption instrument, the Model 303. This was followed by the Australian company, Tektron, which had collaborated with Walsh and CSIRO since 1958, producing the first Australian atomic absorption instrument in 1964.

During the 1960’s and 1970’s, Walsh and his collaborators worked to improve atomic absorption instruments and extend their applications to various fields. In 1969, Walsh was elected a fellow of the Royal Society of London. In 1970, he was awarded an honorary doctor of science degree from Monash University, Melbourne. In 1977, Walsh retired from CSIRO, where he had served as chief research scientist and assistant chief of the division. Soon thereafter, Walsh was knighted for his services to science. Even during retirement, he continued to work as an honorary research fellow and a consultant for several years. Walsh died in Melbourne in 1998.

Impact

Without a doubt, atomic absorption spectroscopy is the most significant advance in elemental analysis in the twentieth century. With the production of the first atomic absorption machines, chemists had an easy and fast method of determining the presence and concentrations of more than sixty-five of the chemical elements in the periodic table. Furthermore the accuracy and sensitivity of this method drove all “wet-chemical” methods into obsolescence. This method also found applications in fields as diverse as medicine, agriculture, food analysis, mineral exploration, metallurgy, enology, environmental science, forensics, and biochemistry. It is not an overstatement to say that all significant chemistry laboratories in the world possess an atomic absorption spectrophotometer. The use of this technology is universal.

Walsh lived and worked at a time when spectroscopy—the study of the interaction of matter with light—was flourishing. Given the rapid advances in the field, no one would have thought that the field needed a new way of looking at problems. Yet Walsh possessed the rare combination of being brilliant, practical, and exceptionally creative. Even during his years at the BNF, Walsh thought that spectroscopy would not advance much further without “a completely new line of attack.” Even though virtually none of his colleagues shared his point of view, Walsh proceeded to gnaw away at the problem until it gave in. The result of his relentless pursuit was a completely new way of determining chemical compositions.

Bibliography

Cazes, Jack, ed. Ewing’s Analytical Instrumentation Handbook. 3d ed. Boca Raton, Fla.: CRC Press, 2004. A rather technical instrumental analysis textbook with an excellent section on atomic absorption spectroscopy that notes Walsh’s seminal contributions to the invention of this technique.

Hannaford, Peter. “Alan Walsh 1916-1998.” Historical Records of Australian Science 13, no. 2 (2000): 179-206. An exhaustive and detailed, but sensitive recollection of Walsh’s life, scientific accomplishment, and personal traits.

Robinson, James W. “A Tribute to Sir Alan Walsh—Development of Atomic Absorption in the United States—A Personal View.” Spectrochimica Acta Part B: Atomic Spectroscopy 54, no. 14 (December, 1999): 1993-1998. A personal encomium of Walsh by an accomplished spectroscopist who knew Walsh personally and collaborated with him.

Walsh, Alan. “The Development of the Atomic Absorption Spectrophotometer.” Spectrochimica Acta Part B: Atomic Spectroscopy 54, no. 14 (December, 1999): 1943-1952. A first-person view of the development of atomic absorption spectroscopy by the man who invented it, told with the wit and wry humor that so characterized him.

Willis, John B. “The Early Days of Atomic Absorption Spectrometry in Clinical Chemistry.” Spectrochimica Acta Part B: Atomic Spectroscopy 54, no. 14 (December, 1999): 1971-1975. A colleague of Walsh tells some very entertaining stories about the development of atomic absorption spectroscopy and highlights the trial-and-error nature of science.