示波极谱法同时测定锌电解液中镉和钴

Study on rapid and simultaneous determination of trace cadmium and cobalt in zinc electrolyte solution by oscillopolarography

研究了pH为 5 0的醋酸 醋酸钠介质中存在大量锌时 ,镉和钴在丁二酮肟 柠檬酸钠 氯化铵体系中的络合物吸附波 .结果表明 ,镉、钴峰电位分别为 - 0 79V和 - 0 93V ,线性范围分别为 0 0 0 5～ 5mg·L- 1 和 0 0 0 0 1～ 0 1mg·L- 1 ,检测限分别为 4 0× 1 0 - 8mol·L- 1 和 8 1× 1 0 - 1 0 mol·L- 1 .该方法具有不经预处理可直接用于锌电解液中微量镉、钴同时测定的优点 .分析了电活性络合物的组成、极谱波性质和电极过程机理 .镉、钴与丁二酮肟 (DMG)的络合比均为 1∶2 ,Cd(DMG) 2 和Co(DMG) 2 络合物均表现出强的吸附特性 ,且前者吸附性更强 ,峰电流主要由络合物中心离子Cd(Ⅱ )和Co(Ⅱ )还原为Cd和Co产生 。

Sensitive adsorptive waves of cadmium(Ⅱ) and cobalt(Ⅱ) dimethylglyoxime NH 4Cl sodium citrate system in the medium of acetate with pH value of 5.0 were studied in the presence of zinc, and the oscillopolarographic method for the rapid and simultaneous determination of trace cadmium and cobalt in zinc electrolyte solution was developed. The peak potentials are at -0.79 and -0.93 V, respectively; the linear ranges of the determinations (0.005～5 mg·L -1 for Cd and 0.000 1～0.1 mg·L -1 for Co), and the detection limits (4.0×10 -8 mol·L -1 for Cd and 8.1×10 -10 mol·L -1 for Co) were determined. The method has directly been used in the rapid and simultaneous determination of the trace cadmium and cobalt in zinc electrolyte liquid mixture with satisfactory results. The method has the advantage of determining the trace cadmium and cobalt in zinc electrolyte solution directly and simultaneous without any pretreatment. The components of the electroactivity complex, the quality of the polarographic wave and the mechanisms of the electrode processes have also been studied. Both the coordination rates of cadmium and cobalt to dimethylglyoxime are 1∶2. The complexes, Cd(DMG) 2 and Co(DMG) 2 all appear to have intense adsorbability, and the former has more intense adsorbability than the latter. The peak currents result mainly from the reductions of the central ions Cd(Ⅱ) and Co(Ⅱ) in the complexes into Cd and Co. Both the polarographic waves are complex adsorption waves.