Ultra-sensitive trace metal analysis of water by laser-induced breakdown spectroscopy after electrical-deposition of the analytes on an aluminium surface

Toxic heavy metals in water pose a potential health and environmental risk to people. The current techniques used for water trace metals analysis are either time-consuming or of low sensitivity. It is necessary to develop a fast and sensitive technique to monitor or analyze trace toxic heavy metals in water. In this work, the trace heavy metals of water were electrically deposited on the surface of a polished high purity aluminium plate and then quantitatively analyzed by laser-induced breakdown spectroscopy (LIBS). It was demonstrated that the electrical-deposition method significantly enhanced the sensitivity of detection by pre-concentration and elimination of water matrix interference. After 10 minutes deposition in 400 mL of water solution with 36 V deposition voltage, the limits of detections of Cr, Mn, Cu, Zn, Cd and Pb were determined to be 0.572, 0.374, 0.083, 5.623, 0.528 and 0.518 mu g L-1, respectively. This approach provides a potential technique to perform direct ultra-sensitive analysis of toxic heavy metals in natural water samples, with the advantages of low cost, high sensitivity and the possibility of analyzing multi-elements simultaneously.