Self-absorption in quantitative glow discharge emission spectrometry

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 de mode in argon, Based on considerations of radiative transfer within the source, and using the two-layer model and other approximations, the equation I-E(M) = REO q C-M(E)M exp (- beta(E)q(M)c(E)(M)) was 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(EO) and beta(E) constants resulting from fitting the experimental data to this relationship were investigated as functions of GD operating conditions, It was shown that R, can be regarded as the (generalized) emission yield, Dependence of the R(EO) and beta(E) parameters on discharge operating conditions suggests that they could reflect more fundamental processes occurring in the discharge, Comparison of beta(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.