修饰铂电极上Cd(Ⅱ)的示波双电位滴定法

Oscillography Double Potentiometric Titration of Cadmium(Ⅱ) Using Modified Platinum Electrode

制备了镉修饰铂电极,用循环伏安法表征了Cd(Ⅱ)在该电极上的吸附特性,探讨了电极的响应机理.通过优化试验条件,建立了一种新的测定Cd(Ⅱ)的示波双电位滴定法.在1.0 mol/L的六次甲基四胺溶液中(pH=6.0),用制备的修饰铂电极作为双指示电极,以EDTA标准溶液滴定Cd(Ⅱ),利用示波器屏幕上荧光点的显著最大位移指示滴定终点.Cd(Ⅱ)在9.0×10-4～3.5×10-3mol/L时,回收率为99.8%～100.3%.该修饰电极具有良好的稳定性和重现性,在含有1.0×10-3mol/L Cd(Ⅱ)的溶液中,连续13次测定,所得终点电位值均在37 mV左右,其相对标准偏差(RSD)0.02%.应用该方法测定含镉样品,RSD值(n=7)小于0.81%,回收率为99.71%～100.09%,测定结果与指示剂法测定值相符.

Cd（II） modified Ptelectrode was prepared and the adsorption character of Cd（II） on the elec- trode was studied by cyclic voltammetry. The mechanism of electrode response was discussed. A new method using oscillopotentiometry for the titration of Cd（II） was described by optimizing the testing condi tions. In 0.1 mol/L hexamethylene tetramine solution （pH 6.0）, Cd（II） was titrated with EDTA, and two modified Ptelectrodes were used as hiindicator electrode system. The end point of titration was determined by an abrupt maximum displacement of the fluorescence spot observed on the screen of the cathodic oscil lograph. When Cd（II） content was in the range of 9.0X 10-4-3.5 X 10-3 mol/L, the recovery was in the range of 99.8%- 100.3%. Furthermore, the modified electrode showed excellent stability and reproducibil ity. In 1.0 - 10-3 mol/L Cd（II） solution, the values of end point potentials obtained from 13 continuous de terminations were all around 37 mV, and the relative standard deviation （RSD） was 0.02%. Moreover, the proposed method has been used in the determination of Cd（II） contained in samples with recoveries of 99.71%- 100.09% and RSD （n=7） less than 0.81%, which are in accordance with the indicator method.