聚L-缬氨酸修饰电极差分脉冲伏安法测定自来水中锌和镉

Determination of trace zinc and cadmium in tap water by differential pulse voltammetry with a polymeric L-valine modified electrode

目的制备聚L-缬氨酸(L-Val))修饰电极,并用于自来水中锌离子和镉离子的快速测定。方法于pH值为5.5的Na,HPO4-NaH,PO4缓冲液中,用循环伏安法(CV)将L-Val电聚合修饰至玻碳电极(GCE)表面,制得聚L-缬氨酸修饰电极(PL-Val/GCE),并用CV法、电化学阻抗法(ESI)对制备的电极性能进行表征。将PL-Val/GCE作为工作电极,建立了差分脉冲伏安法(DPV)测定水中痕量的Zn^2+和Cd^2+。结果在最佳的条件下,Zn^2+和Cd^2+的氧化峰电位分别为-1.184V和-0.872V。Zn^2+峰电流在(5.0x10^-9~2.0x10^-5)mol/L的浓度与其浓度呈良好线性关系,Cd+峰电流在(5.0x10^-9-1.5x10^-7)mol/L和(2.5x10^7-1.0x10^-5)mol/L的浓度与其浓度呈良好线性关系。Zn^2+和Cd^2+的检测限均为2.0x10^-9mol/L。Zn^2+和Cd^2+在自来水样品中的平均回收率在90.0%~105.8%;连续平行测定3次RSD均<4.4%。结论该方法灵敏度高、检测速度快、准确性高,适用于自来水中的Zn^2+和Cd^2+的测定。

Objective The polymeric L-valine (L-Val ) modified electrode was prepared and used for the determination of zinc and cadmium ions in tap water. Methods In the phosphate buffer solution ( pH5.5), L-Val was electropolymerized on the surface of the glassy carbon electrode ( GCE) by cyclic voltammetry ( CV) to obtain a polymeric L-Val modified electrode (PL- Val/GCE). The electrochemical properties of the modified electrode were characterized by CV and electrochemical impedance spectroscopy ( EIS) methods. A differential pulse voltammetry ( DPV ) method was developed for the simultaneous determination of Zn^2+ and Cd^2+ by using PL-Val/GCE. Results Under the optimum conditions, the experimental results showed that the oxidation peaks of Zn2 and Cd2t appeared at -1.184 V and -0. 872 V, respectively. A good linear relationship between the oxidation peak current of Zn^2+ and concentration ( ranging from 5.0 x 10^-9 -2.0 x10^-5 mol/L) can be obtained. While the oxidation peak current of Cd^2+ was linear with the concentration (5.0x10^-9 mol/L-1.5x10^-7 mol/L, 2.5 x10^-7 mol/L-1.0x 10^-5 mol/L). Both of the detection limits for Zn^2+ and Cd^2+ were2.0x 10 ^-9 mol/L. The recoveries of Zn^2+ and Cd^2+ in tap water ranged from 90. 0% to 105. 8%. And RSDs in three detections were all less than 4. 4%. Conclusion The established method is sensitive, fast and accurate. It is suitable for the determination of zinc and cadmium ions in tap water.