Intra-Alkali Matrix Effects in the Inductively Coupled Plasma

Abstract

Spatial profile studies are used to determine the interference effects of alkali matrix elements on the observed emission of alkali analyte elements in the inductively coupled plasma. These interferences are referred to as intra-alkali matrix effects. It is found that significant enhancement of the analyte emission occurs low in the plasma in the initial radiation zone where atomic emission is most intense and that a slight downward shift in the vertical position of the emission peak is caused by the presence of the alkali matrix. A “same value” point occurs in the normal analytical zone where no net effect of the matrix on analyte emission is apparent. In the tail plume of the plasma, some lesser enhancement is again observed. The magnitude of the enhancement effect increases as the ionization potential of the matrix element decreases, and the effect appears linear with matrix concentration. The data suggest that the interference mechanism is related to an increase in electron density in the lower region of the plasma, and analytical correction for the interference is recommended for alkali determinations in the inductively coupled plasma.