Preparing microparticles on an elementary substrate using a micro-hole array sprayer to assist LIBS: a highly sensitive trace rare earth element detection method for aqueous solution analysis

Abstract

Rare earth elements are greatly valued for their crucial role in many high-tech fields. Highly sensitive and precise determination technology of these elements in aqueous solution is essential for the extraction and recycling processes of these elements. Currently, conventional measurement methods for rare earth elements, such as ICP-MS and ICP-OES, often suffer from issues related to complex operations, lengthy procedures, and low economic efficiency. While laser-induced breakdown spectroscopy (LIBS) provides fast and convenient detection capability, due to the matrix effect of the water LIBS technology itself, the reported sensitivities of these elements have not met the application requirements for detection capabilities. In this work, we propose a method that utilizes a micro-hole array sprayer to rapidly prepare rare earth aqueous solution samples into densely and uniformly adhered particles on an Al substrate, combined with a computer-controlled three-dimensional displacement platform to facilitate fully automated LIBS detection. Through optimization of system parameters, the detection limits for La, Pr, Nd, and Sm reach 8.6, 22.3, 13.6, and 6 μg L⁻¹, respectively, with a stable repeatability of 4.96%, within a total sample preparation and detection time of no more than 15 minutes. Compared to existing LIBS-based detection methods, the average detection limits have been reduced by two orders of magnitude, essentially meeting the ppb-level requirements for practical production. This demonstrates the potential of our system to develop into a fast, low-cost, standardized detection technology in the field of rare earth element exploration, mining, and recovery.