Study of matrix effects on rare earth elements in hollow cathode discharges

Abstract

By applying a copper hollow cathode discharge (HCD) to the determination of rare earth elements (REE), matrix effects have been studied. The carrier gas type and the matrix effects caused by other REE (Y, La, Ce, Eu), Group IIA elements (Ca, Sr, Ba) and potassium (KCl, KI) have been examined. The ion:atom line intensity ratios reflecting electron density changes versus matrix composition have been investigated. Argon was found to be a better carrier gas than He for excitation of the analysed REE. The lowered analyte signals caused by the REE matrices (at various mass ratios of analyte to matrix) was relatively small; La was the most interacting matrix element and the Ce and Y matrices were the lowest. The matrix effects of Ca, Sr and Ba increased significantly with a decrease in the relative atomic mass of the element and were very strong for Ca. The matrix effects of KCl and KI were not very significant and both the cation and anion contributed. The HCD has been shown to be a good source for the determination of REE traces in the matrices of other lanthanides. Calcium should be removed from a sample before the determination of the REE traces.