Explanation of matrix effects in the GD-OES spectrum of zinc by charge transfer reactions of Ar+ ions with atoms originating from the cathode

Abstract

In the analysis of Zn–Al and Zn–Cu alloys by GD-OES with the Grimm-type glow discharge in argon, emission yields of Zn II lines are higher for Zn–Al alloys than for Zn–Cu alloys. This matrix effect is explained by variations of the argon ionization degree with the analysed matrix. The variations are caused by asymmetric charge transfer (ACT) reactions of Ar⁺ ions with copper and zinc. ACT with Ar⁺ ions is an important ionization mechanism of zinc, populating the 4p ²P⁰_1/2 and 4p ²P⁰_3/2 levels of the zinc ion, and indirectly, by subsequent deexcitation/excitation, other Zn II levels also. Matrix effects of this type probably also occur for other elements that are subject to ACT reactions with argon ions and attention should be paid if ionic lines of such elements are used in analytical applications of GD-OES.