Elemental Analysis of Heated Soil Samples Using Laser-Induced Breakdown Spectroscopy Assisted with High-Voltage Discharges

Abstract

In this study, a high-voltage (HV) oscillatory square pulse was used to re-excite the laser-induced breakdown spectroscopy (LIBS) signal produced by a nanosecond laser on different loamy soil samples at two different temperatures: ambient and 400 °C. The optimal delay was found for each experimental scheme to maximize the emission signal-to-noise ratio. The detection limits of various contaminants in the soil were studied for different experimental configurations. It was found that the lowest detection limits were achieved by combining HV discharges with LIBS on heated samples, resulting in improvements of up to a factor of 7 compared to LIBS on room temperature samples. Plasma characterization shows that the increased detection sensitivity is due to the rise in plasma temperature and electron density with HV re-excitation, while an increase in removed matter contributes to the emission intensification observed when samples are heated.