修饰铂电极上Bi(Ⅲ)的示波双电位滴定法

Oscillo-Potentiometric Titration of Bismuth(Ⅲ) Using Modified Platinum Electrode

制备了Bi(Ⅲ)修饰铂电极,用循环伏安法表征了Bi(Ⅲ)在电极上的吸附特性,探讨了电极的响应机理。通过优化实验条件,建立了一种测定Bi(Ⅲ)的示波双电位滴定法。在0.1 mol/L的硝酸溶液中(pH=1.0),用制备的修饰铂电极作为双指示电极,以EDTA标准溶液滴定Bi(Ⅲ),利用示波器屏幕上荧光点的显著最大位移指示滴定终点。Bi(Ⅲ)在1.19×10-4～1.44×10-2 mol/L时,回收率为99.8%～100.1%,检出限(S/N=3)为1.0×10-4 mol/L。该修饰电极具有良好的稳定性和重现性,在含有1.0×10-2 mol/L Bi(Ⅲ)的溶液中,连续7次测定,所得终点电位值均在100 mV左右,其相对标准偏差(RSD)为0.04%。应用该方法测定含铋样品,RSD值(n=7)小于0.25%,回收率为99.5%～100.5%,测定结果与指示剂法测定值相符。

Bi（Ⅲ） modified Pt-electrode was prepared and the adsorption character of Bi（Ⅲ） on the electrode was studied by cyclic voltammetry.The mechanism of electrode response was discussed.A method using oscillo-potentiometry for the titration of Bi（Ⅲ） was described.In 0.1 mol/L nitric acid solution（pH=1.0）,Bi（Ⅲ） was titrated with EDTA,and two modified Pt-electrodes were used as bi-indicator 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 oscillograph.When Bi（Ⅲ） content was in the range of 1.19×10-4～1.44×10-2 mol/L,the recovery was in the range of 99.8%～100.1% and the detection limit was 1.0×10-4 mol/L（S/N=3）.Furthermore,the modified electrode showed excellent stability and reproducibility.In 1.0×10-2 mol/L Bi（Ⅲ） solution,the values of end point potentials obtained from 7 continuous determinations were all around 100 mV,and the relative standard deviation（RSD） was 0.04%.Moreover,the proposed method has been used in the determination of Bi（Ⅲ） contained in samples with recoveries of 99.5%～100.5% and RSD（n=7） less than 0.25%,which are in accordance with the indicator method.