Simultaneous detection of heavy metals in solutions by electrodeposition assisted laser induced breakdown spectroscopy

Detection of heavy metals in solutions has been performed using laser-induced breakdown spectroscopy (LIBS) combined with electrodeposition (ED). A polished aluminum (Al) sheet serves as the cathode in the three-electrode system. Four heavy metal ions were concentrated at the same time, namely, copper (Cu²⁺), cadmium (Cd²⁺), chromium (Cr³⁺), and nickel (Ni²⁺). The results of experiments demonstrated that it was more conducive to the enrichment of heavy metal elements when the pH of the solution was in the range of 6–8.5. The smoother the aluminum electrode was polished with the metallographic sandpaper, the better the uniformity of enrichment and the repeatability of the experiment. After optimizing the experimental conditions, the relative standard deviation (RSD) values of a laser single-shot of four polished aluminum electrodes were all below 20%. When the aluminum electrode was polished with 5000-mesh metallographic sandpaper, the RSD value between parallel samples was only 0.03%. The limits of detection of the elements are 4.86 μg/l for Cd²⁺, 2.17 μg/l for Cr³⁺, 2.44 μg/l for Cu²⁺, and 10.49 μg/l for Ni²⁺ after being concentrated in a mixed solution for 15 min, respectively. The results indicated that the LIBS technique coupled with ED could be a reliable and accurate method for the detection of heavy metals in solution.