Walsh, Alan

Atomic absorption spectrophotometry was developed in the 1950s by Dr. Alan Walsh.1 The instrumentation of this method is shown in Figure 6.1. In general, chemical compounds are converted into their atomic constituents, and then the light absorption at a wavelength characteristic of a particular atomic species is determined... 

For many years the observation was of little more than academic interest and that interest resided with the atomic physicist. It was not until 1955 that Alan Walsh, working in Australia, published the first paper demonstrating the use of atomic absorption spectrometry (AAS) as an analytical tool... 

From Walsh PC, Oesterling JE, Epstein JI, et al. The value of prostate-specific antigen in the management of localized prostate cancer. In Murphy G, Khoury S eds. Therapeutic progress in urological cancer. New York Alan R Liss Inc, 1989 27-33. 

Shortly after the first publication on atomic absorption in 1955 by the Australian physicist Alan Walsh (11), isolated researchers built the simple instrumentation required to test the technique. However, there was little interest outside Australia until commercial equipment became available, and problems involving burners and emission sources were solved. Analytically, the major advantage of atomic absorption is that it has almost no spectral and few chemical interferences with its determinations. Chemical separations are thus rarely hecessary and are simple when they are required. 

The production of this book has been the outcome of many hours of discussions over the years. The two coauthors have learned a great deal from each other as well as from our many colleagues, students, and friends. An incomplete list of the most important people to whom we owe debts of gratitude would include Mike Barcelona, Michael Elovitz, Bruce Faust, Chad Jafvert, Karen Marley, Gary Peyton, Frank Scully, Alan Stone, Paul Tratnyek, Lee Wolfe, Ollie Zafiriou, and Richard Zepp. Invaluable help with the manuscript was provided by Jean Clarke, Tori Corkery, Jennifer Nevius, and Heather Walsh. Finally, special thanks are due to the students of Environmental Studies 351 at the University of Illinois, who have provided indispensable suggestions about the subject matter of this book over the years. 

Atomic emission spectroscopy, bom in the mid-19th century, was immediately applied to analyses of minute quantities of chemical elements (see chapter 1). Almost a century later, Alan Walsh (1916-98), Council for Scientific Research in Melbourne, Australia, posed a fundamental question Why were chemical elements anatyzed by emission spectroscopy while... 

In 1953, the Australian Physicist Alan Walsh laid the foundations and demonstrated that atomic absorption spectrophotometry could be used as a procedure of analysis in the laboratory (Willard et al., 1991). The theoretical background on which most of the work in this field was based is due almost entirely to this author (Elwell Gidley, 1966). 

Atomic absorption spectrometry (AAS) is nowadays one of the most important instrumental techniques for quantitative analysis of metals (and some few metalloids) in various types of samples and matrices. The history of atomic absorption spectrometry dates back to the discovery of dark lines in the continuous emission spectrum of the sun by WoUaston in 1802. The lines are caused by the absorption of the elements in the atmosphere of the sun. His work was taken up and further pursued by Fraunhofer in 1814. In 1860, Kirchhoff and Bunsen demonstrated that the yellow hne emitted by sodium salts when introduced into a flame is identical with the so-caUed D-Hne in the emission spectrum of the sun. However, it took nearly one century before this important discovery was transferred into a viable analytical technique. In 1955, Alan Walsh published the first paper on atomic absorption spectroscopy [4]. At the same time, and independently of Walsh, AUce-made and Wilatz pubhshed the results of their fundamental AAS experiments [5, 6]. But it was the vision of Walsh and his indefatigable efforts that eventually led to the general acceptance and commercialisation of AAS instrumentation in the mid-1960s. Further instrumental achievements, such as the introduction of the graphite furnace and the hydride generation technique, in the second half of the 1960s further promoted the popularity and applicability of the technique. 

Welz, B. Heitmann, U. 50 Years after Alan Walsh-AAS redefined. Technical Note, Analytik Jena, Jena, Germany, 2005 (www.analytik-jena.de). 

Atomic absorption spectroscopy (Sir Alan Walsh) Atomic absorption spectroscopy is used to identify and quantify the presence of elements in a sample. 

It was only in 1952 when Alan Walsh, after having worked on the spectrochemical analysis of metals for seven years, and in molecular spectroscopy for another six years, began to wonder why molecular spectra were usually obtained in absorption and atomic... 

As Alan Walsh has presented in his perceptive analysis of the reasons, it seems likely that one reason for neglecting atomic absorption methods was that Bunsen and Kirchhoff s work was restricted to visual observation of the spectra. In such visual methods the sensitivity of emission methods was probably better than that of absorption. Not only was the photographic recording of the spectra more tedious, but also the theory seemed to indicate they would only prove useful for quantitative analysis if observed under very high resolution. But possibly a more fundamental reason for neglecting atomic absorption is related to Kirchhoff s law (1859), which states that the ratio of the emissive power E and absorptive power A of a body depends only on the temperature of the body and not on its nature. Otherwise radiative equihbrium could not exist within a cavity containing substances of different kinds. The law is usually expressed as... 

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