Zhou Ming-Hui, Tian Wei, Zhang Jie-Qiong, Chen Xi, Wu Yan-Xiang, Wang Song-Xue
The Academy of National Food and Strategic Reserves Administration (Former Name: Academy of State Administration of Grain, ab. ASAG) No. 11 Baiwanzhuang Str., Xicheng District Beijing 100037 China
RSC Adv. 2019 Oct 15;9(56):32839-32847. doi: 10.1039/c9ra05587h. eCollection 2019 Oct 10.
In order to achieve rapid on-site screening and solve the problem of rapid pretreatment for the determination of lead (Pb) and cadmium (Cd) in cereals by a portable electrochemical analyzer with disposable screen-printed electrodes (SPEs), a new reliable and simple extraction method for Pb and Cd in cereals was developed. The Pb and Cd in cereals were purified by a mixed solution of 1 mol L potassium iodide (KI)/5% vitamin C (VC)/ethyl acetate after being extracted by 10% HNO, which transfers the Pb and Cd into ethyl acetate after a reaction with KI-VC. Then, the Pb and Cd were eluted from ethyl acetate with 5% HNO and were determined by an electrochemical analyzer with screen printed electrodes. Under the optimized conditions, the matrix calibration curves of Pb and Cd in rice and wheat showed good linear relationships with > 0.996. The method shows a detection limit (LOD) for Cd in rice and wheat of 6.7 μg kg and 11.5 μg kg, and the corresponding values for Pb were 34.9 and 31.1 μg kg, respectively. The relative standard deviation (RSD) was less than 8.7% for Cd and Pb. In addition, the recoveries of the tested reference materials using this method were between 80% and 120%. From sample pretreatment to testing results, the whole process took no more than 25 min, and the operation was simple for operators, green to the environment, cheap in terms of instruments, and above all suitable for on-site detection. The results implied that this portable electrochemical method with new pretreatment may be a good choice for screening Pb and Cd in cereal samples on-site.
为实现快速现场筛查，并解决使用一次性丝网印刷电极（SPE）的便携式电化学分析仪测定谷物中铅（Pb）和镉（Cd）的快速预处理问题，开发了一种新的可靠且简单的谷物中Pb和Cd提取方法。谷物中的Pb和Cd经10%硝酸提取后，用1 mol/L碘化钾（KI）/5%维生素C（VC）/乙酸乙酯混合溶液进行纯化，KI-VC与之反应后将Pb和Cd转移至乙酸乙酯中。然后，用5%硝酸从乙酸乙酯中洗脱Pb和Cd，并用带丝网印刷电极的电化学分析仪进行测定。在优化条件下，大米和小麦中Pb和Cd的基体校准曲线显示出良好的线性关系，相关系数r>0.996。该方法对大米和小麦中Cd的检出限（LOD）分别为6.7 μg/kg和11.5 μg/kg，Pb的相应值分别为34.9和31.1 μg/kg。Cd和Pb的相对标准偏差（RSD）均小于8.7%。此外，使用该方法对测试参考物质的回收率在80%至120%之间。从样品预处理到测试结果，整个过程耗时不超过25分钟，操作对操作人员而言简单，对环境友好，仪器成本低廉，最重要的是适用于现场检测。结果表明，这种具有新预处理方法的便携式电化学方法可能是现场筛查谷物样品中Pb和Cd的良好选择。
