化学学报 ›› 2012, Vol. 70 ›› Issue (06): 765-769.DOI: 10.6023/A1105071 上一篇    下一篇

研究论文

修饰铂电极上Cd(Ⅱ)的示波双电位滴定法

齐蕾a, 齐同喜b   

  1. a 南京大学化学化工学院 南京 210093;
    b 山东理工大学化学工程学院 淄博 255049
  • 投稿日期:2011-05-07 修回日期:2011-11-07 发布日期:2011-12-14
  • 通讯作者: 齐同喜

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

Qi Leia, Qi Tongxib   

  1. a School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093;
    b College of Chemistry and Chemical Engineering, Shandong University of Science and Engineering, Zibo 255049
  • Received:2011-05-07 Revised:2011-11-07 Published:2011-12-14

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9.0×10-4~3.5×10-3 mol/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1.0×10-3 mol/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.

关键词: 示波分析, 双电位滴定法, 修饰铂电极, Cd(Ⅱ), EDTA

Cd(Ⅱ) modified Pt-electrode was prepared and the adsorption character of Cd(Ⅱ) on the electrode was studied by cyclic voltammetry. The mechanism of electrode response was discussed. A new method using oscillo-potentiometry for the titration of Cd(Ⅱ) was described by optimizing the testing conditions. In 0.1 mol/L hexamethylene tetramine solution (pH 6.0), Cd(Ⅱ) 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 Cd(Ⅱ) content was in the range of 9.0×10-4~3.5×10-3 mol/L, the recovery was in the range of 99.8%~100.3%. Furthermore, the modified electrode showed excellent stability and reproducibility. In 1.0×10-3 mol/L Cd(Ⅱ) solution, the values of end point potentials obtained from 13 continuous determinations 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.

Key words: oscillography analysis, double potentiometric titration, modified Pt-electrode, Cd(Ⅱ), EDTA