Laser Spectrometric Techniques in Analytical Atomic Spectrometry

AbstractThe main purpose of this article is to describe the theory, instrumentation, and analytical performance of laser analytical atomic spectrometry, focusing on absorption, fluorescence, and ionization techniques. The structure of the article is such that it first provides an outline of the theory of light‐matter interactions that prevail for each type of technique as well as of the most common modulation techniques, primarily, wavelength modulation (WM). This is followed by a section that covers the most important types of instrumentation used. The article finally provides a detailed discussion on the specific instrumentation, mode of operation, use, performance, and applications (both analytical and diagnostic) of each technique.In terms of laser atomic absorption, the focus of the discussion is on the use of approaches to enhance the detection capability by either reducing the amount of noise (as is done by the wavelength modulation absorption spectrometry (WMAS) technique) or by providing an extended interaction length (giving rise to cavity‐enhanced absorption spectrometry (CEAS) techniques in general, and cavity ring‐down spectrometry (CRDS) in particular). Laser atomic fluorescence techniques (often referred to aslaser‐excited atomic fluorescence spectrometry(LEAFS)) as well as laser ionization techniques (termed eitherlaser‐enhanced ionization(LEI) orresonance ionization spectrometry(RIS)) are also covered in some detail. It is shown that several of these techniques are capable of detecting a variety of elements in liquid samples down to low picogram per milliliter (pg mL−1) or parts‐per‐trillion (ppt) concentrations and in low femtogram amounts. Also other properties of the techniques, e.g. selectivity and linear dynamic range (LDR), are in general superior to those of conventional (nonlaser‐based techniques).