Determination of rare earth elements in liquid-phase samples by superhydrophobic array-assisted spark-discharge LIBS

Rapid determination of rare earth elements (REEs) in liquid-phase samples is of great significance in the fields of ion-adsorption rare earth resource exploration and exploitation, quality control of extraction processes, recycling of rare earth resources, and nuclear industry wastewater monitoring. In order to reduce the detection limit of REEs in liquid samples by laser-induced breakdown spectroscopy (LIBS), superhydrophobic array-assisted spark-enhanced laser-induced breakdown spectroscopy (SHA-SD-LIBS) was used in this study to determine the REEs in liquid-phase samples. Optimal experimental conditions were chosen to measure the REEs with the parameters of La II 394.91 nm, Er 402.051 nm, Ce II 418.66 nm, Nd II 424.738 nm, Gd II 443.063 nm, and Pr 492.46 nm as the characteristic spectral lines, and the calibration curves were established for the quantitative analysis of the solutions of six rare earth elements (La, Er, Ce, Nd, Gd and Pr) with different concentrations. The results show that the fit coefficients R² of the calibration curves were above 0.99. The corresponding detection limits were 0.007 μg/mL, 0.045 μg/mL, 0.011 μg/mL, 0.019 μg/mL, 0.041 μg/mL, and 0.008 μg/mL. The proposed method is a simple, low-cost, and highly efficient way to improve the quality of the liquid-phase sample. Compared with the conventional LIBS method, the proposed method can significantly reduce the detection limit of REEs in liquid phase samples with simple sample preparation and low cost. It can serve as a basis for new rapid and accurate methods of measuring rare earth element types and contents in liquid phase samples.