Study on the online detection of atmospheric sulfur via laser-induced breakdown spectroscopy

Abstract

The LIBS detection of sulfur presents particular difficulty because of the high excitation energy of sulfur element and the relative weakness of spectral lines. In this work, a novel laser-induced breakdown spectroscopy (LIBS) experimental apparatus has been developed for the direct detection of atmospheric sulfur. The measurement of atmospheric sulfur was performed in open air with a laser energy of 1000 mJ and ionic lines in the visible range were successfully observed. Moreover, experiments performed on the sample in different states demonstrated that ionic lines are more likely to appear in the detection of the gaseous sample than the liquid sample under same experimental conditions. In addition, the quantitative detection of sulfur was studied by performing LIBS detection on the standard DMS gas with different concentrations. Also, the calibration model of sulfur was established by fitting the intensity of the line and the concentration of sulfur compounds. The limit of detection (LOD) of LIBS in this work was calculated to be 46 mg L⁻¹. Finally, the molecular structure of the sample was accurately determined via laser Raman spectroscopy with the assistance of first-principles calculation. All results showed that LIBS combined with Raman spectroscopy has great potential in the application of direct online detection of sulfur element in the atmosphere.