Semi-quantitative analysis of binary alloys using laser-induced breakdown spectroscopy and a new calibration approach based on linear correlation

A new calibration approach to analyze binary solid samples at the percentage level is proposed, and its application to laser-induced breakdown spectroscopy (LIBS) is presented. The method is based on the observed dependence of the linear correlation coefficient on the analyte concentration in a binary sample. The linear correlation coefficient is calculated between spectra of a range of certified standards and the spectrum of a reference sample (the analyte in the form of a pure metal), and the resulting curve is used as a calibration curve. It was found that a quadratic function could be adequately used to fit the calibration points. The first part of this paper characterizes the proposed calibration method providing mathematical and simulational data, and also describes a possibility to extend it to multicomponent samples. In the second part, the method is successfully applied to the LIBS analysis of Cu in brass samples as well as Al, Si and Cu in aluminum alloys. The new method was found to give rise to results accurate to 1-5% for major components, and usually outperformed conventional calibration in terms of both precision and accuracy. (C) 2001 Elsevier Science B.V. All rights reserved.