修饰铂电极-示波双电位滴定法测定Zn(Ⅱ)

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

制备了锌修饰铂电极,建立了一种新的测定Zn(Ⅱ)的示波双电位滴定法。在六次甲基四胺溶液(1.0mol/L)中(pH=5.5),用制备的修饰铂电极作为双指示电极,以EDTA标准溶液滴定Zn(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。在3.0×10-4～2.0×10-3mol/L的浓度范围内,Zn(Ⅱ)的回收率为99.9%～100.2%。该修饰电极具有良好的稳定性和重现性,对Zn(Ⅱ,1.0×10-3mol/L)溶液连续11次测定,所得终点电位值均在10.1mV左右,其相对标准偏差(RSD)为0.5%。用来测定含锌的实际样品,其结果与指示剂法测定的值基本一致。

A Zn（Ⅱ） modified Pt-electrode was prepared. A new method using oscillo-potentiometry for the titration of Zn（Ⅱ） was described. In 1.0 mol/L hexamethylene tetramine solution （pH 5.5）, Zn（Ⅱ） was titrated with EDTA, and two modified Pt-electrodes were used as bi-indicator electrode. The end point of titration was determined by the observation of an abrupt maximum displacement of the fluores cence spot on the screen of the cathodic oscillograph. When Zn（Ⅱ） content was in the range of 3.0×10.4^-4～2.0×10^-3 mol/L, the recovery was in the range of 99.9%～100.2%. Furthermore, the modified electrode showed excellent stability and reproducibility. In 1.0 X 10^-3 mol/L of Zn（Ⅱ） solution, the values of end point potentials obtained from 11 continuous determinations were all around 10.1 mV, and the relative standard deviation （RSD） was 0.5%. Moreover, the proposed method has been used in the determination of Zn（Ⅱ） contained in samples and the results are in accordance with that obtained by indicator method.