QuEChERS-液相色谱-串联质谱法测定茶叶中的丁醚脲

目的:建立茶叶中丁醚脲农药残留检测的液相色谱-串联质谱方法。方法:茶叶样品用乙腈提取后所得提取液经过Qu ECh ERS法净化除去杂质。采用乙腈-水(含0.1%甲酸)流动相体系进行洗脱,C_(18)色谱柱进行色谱分离,电喷雾正离子模式电离,多级反应模式监测,外标法定量。结果:采用GB/T 23205—2008《茶叶中448种农药及相关化学品残留量的测定液相色谱-串联质谱法》检测丁醚脲时回收率低的主要原因是其在前处理过程中发生了分解。采用本实验建立的方法,丁醚脲在1.0~500μg/L质量浓度范围内线性良好(r=0.999 9),定量限为0.01 mg/kg。在0.010、1.0、5.0 mg/kg三个添加量水平的平均加标回收率为83.3%~99.4%,相对标准偏差在1.87%~6.30%之间。结论:本方法操作简便,耗时较短,有效避免了前处理过程中丁醚脲分解对检测结果的影响,适用于茶叶中丁醚脲残留的定性及定量分析。

Determination of Diafenthiuron Residue in Tea by QuEChERS-Liquid Chromatography-Tandem Mass Spectrometry

Purpose: To develop a method for the determination of diafenthiuron residue in tea by liquid chromatographytandem mass spectrometry (LC-MS/MS). Methods: The diafenthiuron in tea was extracted by acetonitrile and purified by the quick, easy, cheap, effective, rugged and safe (QuEChERS) method. The separation of the analyte was performed on a C18 column by gradient elution using a mobile phase consisting of acetonitrile and water (containing 0.1% formic acid). The mass spectrometer was operated with electrospray ion source in positive mode (ESI+) by selective reaction monitoring (SRM), and the analyte was quantified by the external standard method. Results: Low recoveries of diafenthiuron obtained by the method described in GB/T 23205?2008 was in part ascribed to the decomposition of diafenthiuron in the pretreatment processes. A good linearity (r = 0.999 9) was observed over the range of 1.0 to 500 μg/L using the new method developed in this study. The limit of quantification (LOQ) was 0.01 mg/kg, and the recoveries at three spiked levels (0.010, 1.0 and 5.0 mg/kg) varied from 83.3% to 99.4%, with relative standard deviations (RSDs) of 1.87%–6.30%. Conclusion: This method is simple and convenient, and it can effectively avoid the influence of diafenthiuron decomposition in the pretreatment process, and thus can be applied for the qualitative and quantitative confirmation of diafenthiuron residue in tea.