提出了分散固相萃取-液相色谱-串联质谱法测定茶叶中12种农药含量的方法。2 g茶叶样品粉末经10 mL乙腈提取,0.4 g乙二胺-N-丙基硅烷(PSA)净化。以Agilent ZORBAX SB-Aq色谱柱为固定相,以乙腈-含5 mmol·L^-1乙酸铵的0.1%(体积分数)甲酸溶液为流动相体系分离12种农药。采用电喷雾离子源正离子模式扫描,多反应监测模式检测,基质匹配混合标准溶液系列绘制工作曲线,外标法定量。结果表明:12种农药的质量浓度在一定范围内与对应的峰面积呈线性关系,检出限(3S/N)为0.3~3 μg·kg^-1;对阴性样品进行3个浓度水平的加标回收试验,回收率为80.0%~118%,测定值的相对标准偏差(n=6)为1.3%~11%;方法用于70份实际茶叶样品分析,苯醚甲环唑、烯酰吗啉、三唑酮、丙环唑、戊唑醇均有检出,检出量为1.1~1 220.0 μg·kg^-1,其中苯醚甲环唑的检出率最高,总检出率为62.9%。

A method for the determination of 12 pesticides in tea by liquid chromatography-tandem mass spectrometry with dispersive solid phase extraction was proposed. The tea sample powder (2 g) was extracted by 10 mL of acetonitrile, and purified by 0.4 g of ethylenediamine-N-propyl silane (PSA). Twelve pesticides were separated by Agilent ZORBAX SB-Aq column as stationary phase and acetonitrile-0.1% (volume fraction) formic acid solution containing 5 mmol·L^-1 ammonium acetate as mobile phase system. Electrospray ion source with positive ion mode was used for scan, multi-reaction monitoring mode was used for detection, and matrix matching mixed standard solution series were used for drawing working curves, with quantification by external standard method. It was shown that linear relationships between the mass concentrations and peak areas of 12 pesticides were kept in definite ranges, with detection limits (3S/N) in the range of 0.3-3 μg·kg^-1. Test for recovery was made on negative sample at 3 concentration levels by standard addition method, giving results in the range of 80.0%-118%, and RSDs (n=6) of the determined values ranged from 1.3% to 11%. The method was applied to analysis of 70 actual tea samples, and difenoconazole, dimethomorph, triadimefon, propiconazole and tebuconazole were detected, with detection amounts in the range of 1.1-1 220.0 μg·kg^-1. The detection rate of difenoconazole was the highest, and the total detection rate was 62.9%.