Background Correction Methods in Atomic Absorption SpectrometryUpdate based on the original article by Margaretha T.C. de Loos‐Vollebregt,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.

Abstract

AbstractAtomic absorption spectrometry (AAS) is based on the absorption of element‐specific primary source radiation by analyte atoms. If part of the radiation is absorbed by molecules or lost owing to scattering, a higher gross absorbance is measured. The difference between the net absorption of the analyte atoms and the measured gross absorbance is calledbackground absorbance. Background absorption and scattering effects have much more serious effects on the results produced in electrothermal atomic absorption spectrometry (ETAAS) than flame atomic absorption spectrometry (FAAS).The amount of incident light deflected or absorbed by nonatomic species must be measured to obtain the correct net absorbance of the analyte atoms only. Perfect background correction (BC) can be obtained only when the background absorbance measurement corresponds exactly in space, time, and wavelength with the atomic absorbance measurement. Since exact coincidence of all three parameters is obviously impossible, it is customary to give priority to the equality in space and to make the difference in time and/or wavelength as small as possible. Although molecular absorption and radiation scattering are both broadband phenomena, there is no spectral range where constant background attenuation can be guaranteed.In all BC systems, two measurements are made. The total or gross absorbance is measured at the wavelength of the atomic absorption line, and the background attenuation is then subtracted to obtain the analyte absorbance. There are several ways in which the nonatomic absorption at the resonance wavelength can be estimated, including continuum‐source (CS) or deuterium‐lamp (D2‐lamp) BC, Zeeman‐effect BC, and pulsed‐lamp or Smith–Hieftje BC correction methods. The principle of each method, the instrumentation, and applications are discussed. D2‐lamp BC is widely used in FAAS and ETAAS. Pulsed‐lamp BC is sometimes used in FAAS but more often in ETAAS. Zeeman‐effect BC is only used in ETAAS.