Correction of Matrix Effects in Quantitative Elemental Analysis With Laser Ablation Optical Emission Spectrometry

Abstract

A new approach to the quantification of the optical emission signals from a laser produced plasma in air at atmospheric pressure is described. It is based on a simple analytical model giving intensity of the emission lines as a function of the vaporized mass and the plasma excitation temperature. Under the hypothesis of a stoichiometric ablation process, these two parameters are presumed to be responsible for the matrix effects observed when the composition of the sample is changed. Under the experimental conditions chosen it is demonstrated that the acoustic signal emitted by the plasma is proportional to the vaporized mass and that the excitation plasma temperature can be controlled using the line ratio of a given element chosen as a ‘temperature sensor’. Normalization of the emission signals by these two parameters allows for an efficient correction of the matrix effects. Results obtained on a series of aluminium alloys, steel and brass samples demonstrate, for the first time, the possibility of matrix independent analysis with LA-OES with an accuracy of a few percent.