Quantitative analysis of mercury in liquid samples using laser-induced breakdown spectroscopy combined with shear thickening fluid

Abstract

Laser-induced breakdown spectroscopy (LIBS) has been widely used to analyze heavy metals in the environment. When LIBS is used to analyze mercury (Hg) in liquids, water splashing, surface ripples, and plasma quenching will reduce analytical sensitivity and accuracy. In this work, a new method that combines shear thickening fluid with LIBS (STF-LIBS) was first proposed to improve the analytical capability of Hg in liquids. In this method, liquid samples were prepared as shear thickening fluid (STF) samples for LIBS detection. The sample preparation takes 30 seconds and needs 1.5 ml of liquid sample. The time evolution of laser-induced plasma plumes and Hg atom line emission intensities of the STF sample were analyzed. The calibration curves of Hg(I)253.65 nm were constructed under the optimized parameters. The results showed that, the evolution time of plasma plumes in the STF sample was 1.57 times longer than that in the liquid drop sample. The emission intensity of Hg(I) 253.65 nm in the STF sample was 3.96 times higher than that in the liquid drop sample under the optimized parameters. According to the calibration curves, the limit of detection (LoD) and coefficient of determination (R²) of STF-LIBS were 0.771 mg L⁻¹ and 0.982, respectively. Compared with direct analysis of liquid drop samples, STF-LIBS improved both the analytical sensitivity and the analytical accuracy of Hg in liquid samples, with the LoD improved by 53.24 times and R² increased by 0.148. The practicability of STF-LIBS was verified by analysis of Hg in rivers and domestic wastewater, and the recovery values were in the range of 91.6–104.9%.