Voltammetric Determination of Trace Amount of Cobalt Using Silver Amalgam Solid Electrode Modified with Dimethylglyoxime

The carbon paste electrode was prepared according to the method described in literature<参考文献原文>,and modified by applying a layer of a paste mixture containing silver powder,dimethylglyoxime and mercury.In the base solution of ammonium citrate and ammonium chloride at pH 6.0,a coordination complex was formed between the dimethylglyoxime of the modified electrode and Co2+ ion,showing a sensitive reduction peak at the potential of -1.18 V (vs.SCE).Values of peak height were found to keep linear relationship with mass concentration of Co2+ ion in the range of 0.10-2.0 mg·L-1,with a detection limit (3s/k) of 0.02 mg·L-1.Based on these facts,a linear scanning-voltammetric method for determination of traces of cobalt ion in water sample was proposed.Precision was tested with 0.10 mg·L-1 Co2+ for 11 determination with a same electrode,value of RSD found was 1.93%.Two water samples were analyzed by this method,and using these samples as matrixes,recovery was tested by standard addition method,giving values of average recovery of 98.8% and 105.1%.