用微型DPSA-1仪结合丝网印刷碳电极(SPCE),以微分电位溶出法对茶叶中的铅、镉、铜进行同步快速检测。优化的试验参数如下：Hg2+浓度为3×10-4 mol/L,支持电解质为1.5 mol/L pH4.0的氯化铵溶液,富集电位-1.1 V,终止电位-0.2 V,富集时间200 s。在此条件下获得的检测结果在20~840 μg/L（相当于茶叶中铅含量为1~42 mg/kg）范围内呈现良好的线性关系,铅的相关系数为r=0.99749,检出限为1.12 μg/L(S/N=3);镉的相关系数为r=0.99740,检出限为1.09 μg/L(S/N=3);铜的相关系数为r=0.99612,检出限为1.23 μg/L(S/N=3)。研究了检测过程中存在多种干扰离子对于铅、镉、铜检测的干扰情况。试验所得检测结果与国标检测法进行t检验,无显著差异。比较常规的检测技术,微型DPSA-1型仪结合SPCE微分电位溶出法同步检测茶叶中的铅、镉、铜,是更加经济的一种快速检测方法,可实现样品的高比例筛检,还可推广应用于其他类型食品和环境样品中铅、镉、铜的同步快速检测。
Mini DPSA-1 device, coupled to screen-printed carbon electrodes (SPCE), was used for simultaneous rapid detection of lead, cadmium and copper in tea by differential potentiometric stripping analysis (DPSA). The optimized experimental parameters were as follows, Hg2+ concentration — 3×10-4 mol/L, supporting electrolyte — 1.5 mol/L pH4.0 NH4Cl, deposition potential — -1.1 V, final potential —-0.2 V, deposition time — 200 s. The potentiometric stripping response for lead, cadmium and copper following 200 s deposition was linear over the concentration range examined (20~840 μg/L) with r values of 0.99749, 0.99740 and 0.99612 and detection limit of 1.12 μg/L, 1.09 μg/L and 1.23 μg/L (S/N=3), respectively. The interferences of various metal ions were also examined in the determination of lead, cadmium and copper. No significant difference existed after the rapid detection results were compared with GB method using t test. In comparing with conventional detection technique, this detection method for lead, cadmium and copper in tea, using mini DPSA-1 instrument, coupled to SPCE by DPSA, was a cheaper rapid detection technique. It could achieve a high percentage of sample screening and be applied to the simultaneous rapid detection of lead, cadmium and copper in other food and environmental samples.
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