茶碱在石墨烯／磷钨酸修饰电极上的电化学行为及测定

Electrochemical Behavior and Determination of Theophylline on the Phosphotungstic Acid / Graphene Modified Electrode

采用滴涂法制备了石墨烯/磷钨酸修饰电极（GO-PTA/GCE），运用循环伏安法研究了茶碱（THEO）在该修饰电极上的电化学行为，并讨论了修饰剂石墨烯和磷钨酸的配比及用量、底液种类及浓度、扫速对其测定的影响。运用交流阻抗法研究修饰前后电极表面的特性。结果表明，在0.02 mol/L H2SO4溶液中，THEO在该修饰电极上于1.185 V出现一不可逆氧化峰，且在100-800 mV/s范围内，其峰电流与扫速平方根（v1/2）呈线性关系，表明该电极过程为受扩散控制的不可逆过程。THEO在该修饰电极上的电子转移数n=1，有效面积A=0.116 9 cm2，扩散系数D =6.675×10-5 cm2/s。在优化实验条件下，采用差分脉冲伏安法对THEO进行定量测定，发现THEO的峰电流与其浓度在6.0×10-7-1.0×10-4 mol/L范围内呈良好的线性关系，检出限可达5.5×10-7 mol/L。采用该法对水样中THEO进行检测，回收率为92.6%-106.3%。

A graphene and phosphotungstic acid modified electrode （GO-PTA/GCE） was prepared by drop coating of graphene and phosphotungstic acid. The electrochemical behavior of theophylline（THEO） was studied on GO-PTA/GCE by cyclic voltammetry,and the influences of ratio of GO to PTA,amounts of GO and PTA,type and concentration of supporting electrolyte,and scan rate on the electrochemical behavior of THEO at GO-PTA/GCE were discussed by cyclic voltammetry. The properties of electrode surface were studied by the nyquist plots. The results indicated that,in 0.02 mol/L H2SO4 solution,there was an irreversible oxidation peak at 1.185 V on the modified electrode.The peak currents were linear with the square root of the scanning rate in the range of 100-800 mV/s,indicating that the electrode process of THEO was irreversible and controlled by diffusion. The electron number（n）,effective area（A） and diffusion coefficients（D） of THEO were calculated to be 1,0.116 9 cm2 and 6.675×10-5 cm2/s,respectively. Under the optimal conditions,the differential pulse voltammetric method was used to determine THEO. A good linear relationship between oxidation peak current and THEO concentration in the range of 6.0×10-7-1.0×10-4 mol/L was observed,and the detection limit was 5.5×10-7 mol/L. The method was successfully applied in the determination of THEO in water samples with recoveries of 92.6%-106.3%.