丁二酮肟沉淀分离-EDTA滴定法测定含镍锌物料中锌

用EDTA滴定法测定锌,当溶液中镍质量浓度高于0.25 μg/mL时,对二甲酚橙(XO)指示剂有封闭作用,从而影响终点判断。而向溶液中加入2倍于镍量的丁二酮肟沉淀分离镍,从而消除镍元素对滴定终点的干扰,在分离镍后的溶液中加入5 g碘化钾掩蔽镉,用EDTA标准溶液直接滴定锌含量,滴定终点现象正常。按照实验方法对模拟样品试液中锌进行测定,回收率在99.02%~100.24%之间。实验方法用于测定两个含镍锌物料样品中锌,结果的相对标准偏差(RSD,n=11)小于1%,与氢氧化钠沉淀分离-EDTA滴定法测定锌的结果相一致。

Determination of zinc in zinc-bearing material containing nickel by EDTA titration after precipitation separation using dimethylglyoxime

The content of zinc was determined by EDTA titration. When the mass concentration of nickel in solution was higher than 0.25 μg/mL, it showed closing effect on the xylenol orange (XO) indicator, which influenced on the judgment of endpoint. The dimethylglyoxime with double amount of nickel was added into solution for the precipitation separation of nickel. Thus the interference of titration end point by nickel could be eliminated. After separation of nickel, 5 g of potassium iodide into solution was added to mask cadmium. The content of zinc was directly titrated by EDTA standard solution. The titration endpoint was normal. The content of zinc in simulated sample solution was determined according to the experimental method. The recoveries were between 99.02% and 100.24%. The proposed method was applied to the determination of zinc in two materials containing nickel and zinc. The relative standard deviations (RSD, n=11) were less than 1%. The found results were consistent with those obtained by EDTA titration after precipitation separation using sodium hydroxide.