Gui Ting, Jia Gui F, Xu Jin, Ge Shi J, Long Xiao F, Zhang Yu P, Hu De Y
a State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education , Guizhou University , Guiyang , People's Republic of China.
J Environ Sci Health B. 2019;54(4):326-335. doi: 10.1080/03601234.2019.1571361. Epub 2019 Feb 17.
A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method was developed for the determination of thiamethoxam and its metabolite clothianidin in citrus (including the whole citrus, peel and pulp) and soil samples by liquid chromatography-tandem mass spectrometry. The sample was extracted with acetonitrile and purified with octadecylsilane. The detection limits of both compounds were 0.0001-0.0002 mg kg, while the limit of quantification of thiamethoxam was 0.002 mg kg and the limit of quantitation of metabolites was 0.001 mg kg. The recovery was 70.37%-109.76%, with inter-day relative standard deviations (RSD) (n = 15) values ≤9.46% for the two compounds in the four matrices. The degradation curve of thiamethoxam in whole citrus and soil was plotted using the first-order kinetic model. The half-life of the whole citrus was 1.9-6.2 days, and the half-life of the soil was 3.9-4.2 days. The terminal residue of thiamethoxam (the sum of thiamethoxam and clothianidin, expressed as thiamethoxam) was found to be concentrated on the peel. The final residual amount of thiamethoxam in the edible portion (pulp) was less than 0.061 mg kg. The risk quotient values were all below 1, indicating that thiamethoxam as a citrus insecticide does not pose a health risk to humans at the recommended dosage.
建立了一种改进的快速、简便、廉价、高效、耐用且安全（QuEChERS）的方法，用于通过液相色谱-串联质谱法测定柑橘（包括整个柑橘、果皮和果肉）和土壤样品中的噻虫嗪及其代谢物噻虫胺。样品用乙腈萃取，并用十八烷基硅烷净化。两种化合物的检测限均为0.0001110.0002 mg/kg，而噻虫嗪的定量限为0.002 mg/kg，代谢物的定量限为0.001 mg/kg。回收率为70.37%-109.76%，四种基质中两种化合物的日间相对标准偏差（RSD）（n = 15）值≤9.46%。采用一级动力学模型绘制了噻虫嗪在整个柑橘和土壤中的降解曲线。整个柑橘的半衰期为1.9-6.2天，土壤的半衰期为3.9-4.2天。发现噻虫嗪的最终残留（噻虫嗪和噻虫胺之和，以噻虫嗪表示）集中在果皮上。可食用部分（果肉）中噻虫嗪的最终残留量小于0.061 mg/kg。风险商值均低于1，表明噻虫嗪作为柑橘杀虫剂在推荐剂量下对人类不存在健康风险。
