A quantitative analysis method for LIBS methane detection based on C and CN line competition—MEWE-SC equation

Abstract

The real-time in situ detection and quantitative analysis of atmospheric methane have always been challenging work. In this study, a promising detection-analysis system and a calibration method for methane quantitative detection in the atmosphere were developed using laser-induced breakdown spectroscopy (LIBS) and a multidimensional entropy weight empirical based on the spectral competition equation (MEWE-SC equation), which is proposed for the first time. Static methane under normal air conditions was detected with carbon and hydrogen in the spectrum being contrastively analyzed. Then, the dynamic methane spectrum was detected by controlling the gradient change in methane concentration. The dynamic methane spectrum illustrated the change law of line C I and CN band. Afterwards, the Lomakin–Scheibe empirical equation was adopted to build the quantitative model. Having considered the C I and CN line competitions, a multidimensional entropy weight empirical based on the spectral competition equation was developed, realizing the high accuracy of quantitative fitness. The innovative method derived from LIBS and line competition theory is fast and in situ, showing far-reaching application prospects in the real-time quantitative detection of methane and some other gases containing carbon.