Heavy metals high-sensitive detection by laser-induced breakdown spectroscopy based on radial electroosmotic flow-driven enrichment.

Heavy metal detection is imperative for human health and environmental sustainability. However, the commonly used liquid sample pretreatment, drying liquid droplet to solid, encounters solute diffusion and nonuniform distribution, thus causing unpromising detection results. Here, we developed a radial electroosmotic flow-driven (REOF) platform to enrich heavy metals in water for high-sensitive detection using laser-induced breakdown spectroscopy (LIBS). Firstly, the electrodes in the substate for REOF were designed and produced by the printed circuit board manufacturer. Different particle deposition patterns were observed by modifying the direction and magnitude of voltage in the evaporated droplets of Cadmium Chloride (CdCl) on the substrate. Then, the two-dimensional model of the evaporating droplets with REOF was established to verify the experimental phenomenon. The CdCl (10-50 mg/L) and Manganese Chloride (MnCl, 1-8 mg/L) solutions were quantitatively analyzed with the optimized parameter on the substrate by LIBS. The detection limits of Ca and Mn can be reduced by approximately 42 times with REOF substrates by LIBS. Finally, the Mn in the real underground water sample was tested with the REOF substrate by LIBS, and the relative error was 5.5% compared with the results of ICP-MS. The results demonstrated that the REOF can enrich and uniformly distribute the solute on the substrate, and be helpful for the analysis of heavy metals in solution with LIBS.