Determination of copper,lead,cadmium and nickel in zinc electrolyte by differential pulse stripping voltammetry
MU Peng-tao1, SHEN Qing-feng2, YU Xiao-hua2, XU Shuang-quan2, LIU Chun-xia*1
1.Research Center for Analysis and Measurement,Kunming University of Science and Technology,Kunming 650093,China; 2.Faculty of Metallurgical and Energy Engineering,Kunming University of Science and Technology,Kunming 650093,China
Abstract：The determination method of trace Cu2+, Pb2+, Cd2+ and Ni2+ by differential pulse stripping voltammetry without pre-separation was established. In ammonia water-ammonium chloride system, Zn2+ was masked by ammonia water, and Ni2+ was complexed by dimethylglyoxime (DMG). This system could eliminate the interference of much Zn2+ to the determination of Ni2+ and Cd2+. The stripping peak potential for Cu2+, Pb2+ and Cd2+ was -0.28,-0.47 and-0.63 V, respectively, under the following experimental conditions: the initial potential was -0.80 V, the terminal potential was-0.1 V, the accumulation potential was -0.85 V, the accumulation time was 100 s, the scanning rate was 0.015 V/s, and 0.5 mL of ammonia water-ammonium chloride solution was added. The mass concentration in range of 2.0×10-6-1.0×10-3, 1.6×10-6-6.6×10-3 and 2.3×10-6-1.1×10-2 g/L for Cu2+, Pb2+ and Cd2+ showed good linear relationship to the peak current. The detection limit was 8.9×10―8, 8.1×10―7 and 2.1×10―7 g/L, respectively. If the solution was not replaced, and 0.5 mL of DMG and 0.6 mL of ammonia water were added into solution, the stripping peak potential for Ni2+ was -1.03 V under the following conditions: the initial potential was -0.90 V, the terminal potential was -1.2 V, the accumulation potential was -0.80 V, the accumulation time was 40 s and the scanning rate was 0.015 V/s. The mass concentration of Ni2+ in range of 1.0×10―6-5.6×10―4 g/L showed good linear relationship to the peak current. The detection limit of method was 4.6×10-7 g/L. The common ions in solution did not interfere with the determination of Cu2+, Pb2+, Cd2+ and Ni2+. The content of Cu2+, Pb2+, Cd2+ and Ni2+ in mixed standard solution was determined by standard addition method. The relative standard deviations (RSD, n=6) were between 0.075% and 1.8%. The recoveries were between 90% and 109%. The proposed method was applicable for the determination of actual samples of zinc sulfate electrolyte and neutral liquid supernatant. The found results of neutral liquid supernatant were consistent with those obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES).
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