基于石墨烯/纳米氧化铝修饰电极的溶出伏安法测定土壤中铜

制备了一种石墨烯/纳米氧化铝复合膜修饰玻碳电极以测定土壤中铜含量。采用阳极溶出伏安法考察了水溶液中铜在裸电极和不同膜修饰电极上的电化学行为,并对实验条件进行了优化。结果表明,在pH 4.6 的磷酸氢二钠-柠檬酸缓冲液(简称Mc缓冲溶液)中,于-0.6V的富集电位下富集12min,铜在复合膜修饰电极上的溶出峰电流相对于裸玻碳电极提高了2.4倍,铜的溶出峰电流与其浓度在6×10^-9~1×10^-5 mol/L范围内呈良好的线性关系,检出限达到1×10^-9 moL/L。最后用石墨烯/纳米氧化铝复合膜修饰电极检测微波消解后土壤样品中铜的含量,6次平行测定相对标准偏差(RSD)均小于5%,土壤样品中铜的质量分数介于24.86~36.04mg/kg之间,表明该小区土壤中铜的含量位于正常水平。同时采用火焰原子吸收光谱法(AAS)进行方法对照,检测结果为25.47~35.86mg/kg,表明实验方法比较可靠。

Determination of copper in soil by stripping voltammetry based on graphene/nano aluminum oxide modified electrode

A graphene/nano aluminum oxide composite membrane modified glassy carbon electrode was prepared to determine the copper content in soil. The electrochemical behaviors of copper in solution on bare electrode and different modified electrodes were investigated by stripping voltammetry. The experimental conditions were optimized. The results showed that the stripping peak current of copper on composite membrane modified electrode increased by 2.4 times compared to that on bare glassy carbon electrode after enrichment at -0.6V for 12min in disodium hydrogen phosphate-citric acid buffer solution at pH 4.6 (Mc buffer solution). Moreover, the stripping peak current of copper had good linear relationship with its concentration in range of 6×10^-9-1×10^-5 mol/L. The detection limit was 1×10^-9 moL/L. The content of copper in soil sample after microwave digestion was determined using graphene/nano aluminum oxide composite membrane modified electrode. The relative standard deviations (RSD n=6) were less than 5%. The mass fractions of copper in soil sample were between 24.86mg/kg and 36.04mg/kg, indicating that the copper content in soil in this region was at normal level. Meanwhile, the samples were also determined by flame atomic absorption spectrometry (AAS), and the found results were 25.47-35.86mg/kg. Therefore, the proposed method was reliable.