Self-absorption in Quantitative Glow Discharge Emission Spectrometry

Abstract

The emission intensities of five resonance atomic lines affected by self-absorption were investigated as a function of analyte concentration in a sample for a Grimm-type atomization/excitation source operated in the dc mode in argon. Based on considerations of radiative transfer within the source, and using the two-layer model and other approximations, the equationwas derived, linking the emission intensity I _E ^M , the sputter rate q ^M and the analyte concentration c _E ^M in the matrix, where E is a particular element in a matrix M . The R _E0 and β _E constants resulting from fitting the experimental data to this relationship were investigated as functions of GD operating conditions. It was shown that R _E0 can be regarded as the (generalized) emission yield. Dependence of the R _E0 and β _E parameters on discharge operating conditions suggests that they could reflect more fundamental processes occurring in the discharge. Comparison of β _E factors for different lines, however, leads to results that are not explicable within the adopted model. Methodology of quantitative GD-OES analysis was generalized to be applicable also to self-absorption lines with non-linear intensity responses.