Abstract: 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.

Key words: chromatography-mass spectrometry, glyphosate, aminomethyl phosphonic acid, green tea