Abstract:

A method was developed for the determination of glyphosate (GLY) and glufosinate-ammonium (GLUF) in tea using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample was extracted with ultrapure water and dichloromethane for 30 min under ultrasonication, followed by a simple cleanup with a C₁₈ solid phase extraction (SPE) cartridge, and then GLY and GLUF were derivatized using 9-fluorenylmethoxycarbonyl (FMOC-Cl) in borate buffer for 2 h. The derivatives of GLY and GLUF were separated on a Waters C₁₈ column (50 mm×2.1 mm, 1.7 μm) in a gradient elution mode, and finally detected with positive electrospray ionization-mass spectrometry (ESI-MS/MS) in multiple reaction monitoring (MRM) mode. The quantification analysis was performed by external standard method. The method showed a good linearity (r> 0.990) in the range of 0.003125-0.1 mg/L. The limits of detection (LODs) of GLY and GLUF were 0.03 mg/kg. At the spiked levels of 0.375, 1.5 and 4.5 mg/kg, the recoveries of GLY and GLUF were 87.37%-99.11% and 81.44%-86.17% respectively, and the relative standard deviations (RSDs) (n=6) of GLY and GLUF were 0.68%-1.35% and 1.01%-2.33%, respectively. This method is simple, rapid and characterized with acceptable sensitivity and accuracy to meet the requirements for the analysis of GLY and GLUF simultaneously in tea.

Key words: glufosinate-ammonium (GLUF), glyphosate (GLY), pre-column derivatization, tea, ultra high performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS)