材料期刊网

制备了用EDTA修饰的铂电极,用循环伏安法检测了修饰电极的电化学性能,对电极响应机理进行了探讨.在以镍(Ⅱ)标准溶液滴定EDTA溶液的示波电位滴定中,用制备的两铂修饰电极作为双指示电极,利用示波器屏幕上荧光点的突然最大位移指示滴定终点.取4.00 mg镍(Ⅱ)按此方法连续测定17次,终点电位值均在34 mV左右,其相对标准偏差(RSD)为0.01%.方法的线性范围为0.16～2.6 mg/mL,检出限为0.013 6 mg/mL.滴定操作在pH 5.5～6.1的六次甲基四胺溶液中进行,用NH_4F、酒石酸钾钠掩蔽Co~(2+)、Fe~(3+)、Al~(3+)、Ca~(2+)、Mg~(2+).应用该方法测定含镍(Ⅱ)样品,RSD值(n=7)小于0.07%,回收率为99.2%～99.6%,与重量方法对照,结果基本一致.

EDTA-modified platinum electrode was prepared and its electrochemical behavior was studied by cyclic voltammetry. The mechanism of electrode response was discussed. Two of such modified Pt-electrodes were used as bi-indicator electrode system in the oscillo-potentiometric titration of Ni(Ⅱ) with EDTA. End point of the titration was determined by an abrupt maximum displacement of the fluorescence spot observed on the screen of the cathodic oscillograph. Repeatability of the modified Pt-e-lectrode was tested by 17 successive determinations of 4. 00 mg of Ni(Ⅱ). The values of end-point potentials obtained were around 34 mV with a RSD of 0.01%. The linear range is 0.16-2.6 mg/mL and detection limit is 0. 013 6 mg/mL. The titration was performed in a hexamethylenetetramine buffer at pH 5.5-6.1.NH_4F and potassium sodium tartrate were used to mask Co~(2+) , Fe~(3+) , Al~(3+) , Ca~(2+) and Mg~(2+) . The proposed method has been used in the determination of Ni(Ⅱ) in samples with recoveries of 99.2%-99.6% and values of RSD (n = 7) less than 0. 07%. The determination results were in accordance with those of gravimetric method.