Topics In..
I
. Chemical lnstrumentutioe
T h e art&, mast of rvhieh are lo be cati-tb~led by p x t authors, are inlended lo s m e the readers of this JOWNAL by calling atlentirm lo nau developments i n the lhewy, design, or auaihbilily of c h i c $ laboralmy instrumenlalion, or by presenting useful insights and explanations of topics lhal are of practical importance to those who use, m leach lhe use of, modern instrumentatia and instrumental lechniques.
XXV. Instrumentation for Atomic Absorption-Part
One
Herbert 1. Kahn, Perkin-Elmer Corporation, Norwalk, Connecticut Dwing the past year, atomic absorption spectrophotametry has made a very important stride as a. technique for determining the concentration of metallic elements. It has ceased to be the wave of the future and become the wave of the present. At this time, well over 1,OW atomic absorption spectrophotometers are in use in North America, more than double the number employed 12 months ago. Shortly after the first publication a n atomic absorption in 1955 by the Australian physicist Alan Walsh (I), isolated researchers built the simple inst,rumentation required to test the technique. However, there was little interest ontside Australis, until cammercial equipment became available, and problems involving burners and emission sources were solved. Even today, the progress of the atomic absorption method is due mainly to government and commercial interest; university scientists have been making only relatively minor rontrihutions. The reason far this quiescence on the part of educators may be that atomic absorption is, a t least on the surface, too simple to be interesting. Instrumentslly, even the most advanced atomic absorption unit is trivial when compared to a mass spectrometer or neutron activation equipment. Andytically, the major advantage of atomic absorption is that i t has no spectral and few chemical interferences with its determinations. Chemical seprtre tions are thus rarely necessary, and are simple when they are required; there is no such thing as "interpretation" of the results.
Instrumental Principle The basic principle of atomic absorption ran well be described as the inverse of that of emission methods for determining metallic elements. In all emission techniques (flame, arc and spark, X-ray fluorescence, and neutron activation)
the sample iq somehow excited in order to make it give off radiation of interest. At the same time, the sample cannot be prevented from giving off radiation which is not of interest. The appropriate type of filtering system is employed to select the radiat,ion which the analvst wants: the r w I ~ ~ l ~u .~t .wn~ - ~ ti
