气相色谱-质谱法测定绿茶中草甘膦和氨甲基膦酸残留量

采用气相色谱-质谱联用建立了一种检测绿茶中草甘膦及其代谢物氨甲基膦酸残留量的测定方法。绿茶样品用水提取,经二氯甲烷液液分配和阳离子交换/反相吸附复合固相萃取柱净化,与三氟乙酸酐和七氟丁醇进行衍生化反应后,由气相色谱-质谱联用仪进行检测。该方法草甘膦定量限为0.05 mg·kg^-1,在2~100 ng·mL^-1浓度范围内呈现良好线性（R²=0.999 3）,氨甲基膦酸的定量限为0.02 mg·kg^-1,在1~100 ng·mL^-1浓度范围内呈现良好线性（R²=0.999 2）。绿茶样品草甘膦添加浓度为0.25 mg·kg^-1和0.50 mg·kg^-1时,其平均回收率分别为90.8%和93.2%,相对标准偏差分别为4.93%和6.74%,氨甲基膦酸添加浓度为0.10 mg·kg^-1和0.20 mg·kg^-1时,其平均回收率分别为85.8%和95.4%,相对标准偏差分别为10.5%和5.16%。该方法净化效果好,杂质干扰小,回收率高,可满足绿茶中草甘膦及其代谢物氨甲基膦酸的残留检测要求。

Determination of Glyphosate and Aminomethyl Phosphonic Acid Residue in Green Tea by Gas Chromatography-Mass Spectrometry

An efficient method for the determination of glyphosate and its metabolite aminomethyl phosphonic acid (AMPA) in green tea was developed based on gas chromatography-mass spectrometry (GC-MS). Green tea samples were extracted with water, preliminary purified by dichloromethane and followed by purification with PCX and HLB combined solid phase extraction columns, derived with trifluoroacetic anhydride (TFAA) and 2,2,3,3,4,4,4-heptafluoro-1-butanol (HFB), then determined by GC-MS. For glyphosate, the limit of quantification (LOQ) was 0.05 mg·kg^-1, showing good linearity with coefficient R²=0.999 3 in the concentration range from 2-100 ng·mL^-1. For AMPA, itsLOQ was 0.02 mg·kg^-1, showing good linearity with coefficient R²=0.999 2 in the concentration range from 1-100 ng·mL^-1. At the spiked levels of 0.25 mg·kg^-1 and 0.50 mg·kg^-1, the average recoveries of glyphosate in green tea were 90.8% and 93.2%, with relative standard deviation (RSD) of 4.93% and 6.74%. At the spiked levels of 0.10 mg·kg^-1 and 0.20 mg·kg^-1, the average recoveries of AMPA in green tea were 85.8% and 95.4%, with RSD of 10.5% and 5.16%. The proper impurity purification, small impurity interference and high recovery rate made this method suitable for residue detection of glyphosate and its metabolite APMA in green tea.