On-Site Quantitative Elemental Analysis of Metal Ions in Aqueous Solutions by Underwater Laser-Induced Breakdown Spectroscopy Combined with Electrodeposition under Controlled Potential

We propose a technique of on-site quantitative analysis of Zn2+ in aqueous solution based on the combination of electrodeposition for preconcentration of Zn onto a Cu electrode and successive underwater laser-induced breakdown spectroscopy (underwater LIBS) of the electrode surface under electrochemically controlled potential. Zinc emission lines are observed with the present technique for a Zn2+ concentration of 5 ppm. It is roughly estimated that the overall sensitivity over 10 000 times higher is achieved by the preconcentration. Although underwater LIBS suffers from the spectral deformation due to the dense plasma confined in water and also from serious shot-to-shot fluctuations, a linear calibration curve with a coefficient of determination R2 of 0.974 is obtained in the range of 5–50 ppm.