阳极溶出伏安法测定氯化锌-氯化铵电解制锌体系中铅和镉

采用阳极溶出伏安法,建立了在ZnCl₂-NH₄Cl体系中,使用乙二胺四乙酸二钠(EDTA)和磺基水杨酸消除Cu²⁺对Pb²⁺测定的影响,不经预分离同时测定溶液中Pb²⁺和Cd²⁺的方法。在扫描电位为-0.80～-0.30 V、富集电位为-0.85 V、富集时间为100 s、扫描速率为0.015 V/s的优化试验条件下,Pb²⁺和Cd²⁺分别在-0.48 V和-0.68 V处有灵敏的溶出峰。溶液中可能存在的常见离子不干扰测定。Pb²⁺、Cd²⁺浓度分别在9.7×10^-9～2.4×10^-4、1.8×10^-8～8.9×10^-5 mol/L范围内与其峰电流呈良好的线性关系,相关系数分别为0.995和0.998。方法中Pb²⁺、Cd²⁺的检出限分别为3.9×10^-9、1.9×10^-9 mol/L。采用实验方法测定了ZnSO₄电解液和ZnCl₂-NH₄Cl电解液中的Pb²⁺和Cd²⁺,结果的相对标准偏差(RSD,n=6)分别为0.83%～2.1%、0.56%～0.75%,回收率分别为89%～108%、92%～104%。

Determination of lead and cadmium in zinc chloride-ammonium chloride electrolyte system by anodic stripping voltammetry

The simultaneous determination of Pb²⁺ and Cd²⁺ in ZnCl₂-NH₄Cl system by anodic stripping voltammetry was established without pre-separation. The influence of Cu²⁺ on the determination of Pb²⁺ was eliminated using ethylene diamine tetraacetic acid (EDTA) and sulfosalicylic acid as masking agent. The optimal determination conditions were as follows: the scanning potential was -0.80~-0.30 V, the enrichment potential was -0.85 V, the enrichment time was 100 s, and the scanning rate was 0.015 V/s. Pb²⁺ and Cd²⁺ showed sensitive stripping peaks at -0.48 V and -0.68 V, respectively. The common ions in solution had no interference with the determination. The concentration of Pb²⁺ and Cd²⁺ in range of 9.7×10^-9-2.4×10^-4 and 1.8×10^-8-8.9×10^-5 mol/L showed good linearity to the peak current. The correlation coefficient was 0.995 and 0.998, respectively. The detection limit of Pb²⁺ and Cd²⁺ was 3.9×10^-9 and 1.9×10^-9 mol/L, respectively. The content of Pb²⁺ and Cd²⁺ in ZnSO₄ electrolyte and ZnCl₂-NH₄Cl electrolyte was determined by the proposed method. The relative standard deviation (RSD, n=6) was 0.83%-2.1% and 0.56%-0.75%, and the recoveries were 89%-108% and 92%-104%, respectively.