二阶导数催化极谱法选择性测定锌电解液中痕量钴

摘要

We report herein a highly selective method for directly determining the trace Co2+in highly concentrated zinc electrolyte. This novel method is based on a second derivative wave of catalytic adsorptive polarography generated by complexing Co2+ with dimethylglyoxime and nitrite onto a dropping mercury electrode. By employing a medium with NH3-NH4Cl buffer, DMG and NaNO2 during determining the trace Co2+, any interferences of highly concentrated Zn2+and other coexisting metal ions in the electrolyte are completely eliminated due to the selective masking effect of EDTA. When the concentration of Co2+ is within 1.0×10–10–3.2×10–7 mol/L range, it shows a good linear relationship with the current peak. Detection limit is 1.0×10–11 mol/L, and RSD ≤2.7％ for six successive assays. We have compared the efficiency of the current method to that obtained by cobalt nitroso-R-salt spectrophotometry, and the absolute values of relative deviations are ≤4.2％. The method developed and described herein has been successfully employed in determining the trace Co2+ in actual zinc electrolyte.%本文报道了一个直接测定高浓度锌电解液中痕量钴的选择性方法.该方法基于测定Co2+在滴汞电极表面与丁二酮及亚硝酸盐络合产生的催化吸附极谱的二阶导数波建立起来的.利用NH3–NH4Cl缓冲剂,DMG及NaNO2组成的底液测定痕量钴时.由于EDTA的选择性掩蔽作用,电解液中高浓度锌及任何其他金属离子的干扰都能完全排除.当Co2+浓度在1.0×10–10～3.2×10–7 mol/L范围时,与峰电流有良好的线性关系,检出限为1.0×10–11 mol/L,RSD≤2.7％.将本法与亚硝基红盐显色法测定的结果进行了比较,相对偏差的绝对值≤4.2％.本文提出的方法已成功用于实际锌电解液中痕量钴的测定.