Instrumentation S. R. Koirtyohann M. L. Kaiser Department of Chemistry and The Environmental Trace Substances Research Center University of Missouri Columbia, Mo. 65211
Furnace Atomic Absorption— A Method Approaching Maturity The seven ages of an analytical method are conception, verification, instrument development, maturity, applications, broad acceptance, and senescence, according to H.A. Laitinen (1 ). He stated that a method matures when "detailed studies of principle and mechanisms are pursued with the aid of improved instrumentation.... This stage represents the crest of analytical research as distinguished from instrumentation research." From one perspective this accurately describes the current status of furnace atomic absorption (FAA), but there are two ways in which the method doesn't act its age. Applications, an age that normally follows maturity, have been quite extensive for well over a decade. Also, one would expect a mature method to have a generally accepted name. Various names are found in the literature, many of which we object to because of negative descriptors (flameless, nonflame) or because they are lengthy and indirect (electrothermal atomizers, heated graphite atom-
izers). The name we use here is simple, accurate, and direct. Besides, what is wrong with calling a furnace a furnace? The first description of a furnace designed for analytical atomic absorption was by L'vov (2) in 1961. Later, Woodriff and Ramelow (3) described a different furnace design. Neither of these led to popular acceptance of the method because L'vov's work came too early and Woodriff s design was complex. Massmann (4) introduced a much simpler furnace in 1968, and modifications of it became the basis for commercial development and popularization of the method. Massmann's furnace was similar to earlier ones in providing sensitivities in the picogram range, but it differed in that it was heated cyclically rather than having a constant high temperature. Temperature cycling simplified the design, reduced power consumption, and made the system less prone to contamination problems, but at a price. Vaporization, atomization, and
measurement were not separated in time or space. This resulted in severe background absorption problems and matrix-dependent changes in working curve slope. In a sense, it represented a step backward to some of the problems of arc-spark spectroscopy, which had been happily left behind as people converted to flame AA. To make matters worse, furnaces were in the hands of a new generation of users (many had never seen a spectrograph) who were quite unprepared to cope with these effects. Background problems were handled reasonably effectively by simultaneous continuum source correctors (5, 6), though limitations of that approach soon became evident. Many attempts to overcome matrixdependent working curve slope problems were made, but most labs simply lived with them, relying on standard additions for quantitative work. Developments in several areas have brought dramatic improvements in FAA performance, starting about five years ago and accelerating in the last
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Figure 1. Schematic illustration of a furnace for atomic absorption 0003-2700/82/A 351-1515$01.00/0 © 1982 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 54, NO. 14, DECEMBER 1982 · 1515 A
