Determination of Glufosinate, Glyphosate and Its Metabolite Aminomethylphosphonic Acid Residues in Soil by UHPLC-Triple Quadrupole Mass Spectrometry after Purification with Solid Phase Extraction

A method of UHPLC-triple quadrupole mass spectrometry after purification with solid phase extraction was established for determination of glufosinate, glyphosate and its metabolite aminomethylphosphonic acid in soil. Soil sample was mixed with water and dichloromethane, and homogenized at high speed for 1 min. After centrifugation, 3 mL of the supernatant was passed through Oasis HLB solid phase extraction cartridge, and the last 1 mL of eluent was collected, and filtered by 0.22 μm filtering membrane. The contents of glufosinate, glyphosate and its metabolite aminomethylphosphonic acid in the filtrate were determined by UHPLC-triple quadrupole mass spectrometry. In chromatographic analysis, a mixed solution composed of 5 mmol·L^-1 ammonium acetate (adjusting pH to 12 with ammonia) and acetonitrile with various volume ratios was used as the mobile phase for gradient elution, and the Dikma Polyamino amino chromatograhpic column was used as the stationary phase for chromatographic separation. ESI with negative ion mode and MRM mode were used for determination by mass spectrometry. The working curves were made with the matrix-matched mixed standard solution series. The results showed that the linearity ranges of the working curves of glufosinate, glyphosate and aminomethylphosphonic acid were 0.005-0.5 mg·L^-1, 0.01-1.0 mg·L^-1, 0.01-1.0 mg·L^-1, with their detection limits (3S/N) of 0.01, 0.02, 0.02 mg·kg^-1, respectively. The spiked recovery was made on the soil samples at 3 concentration levels, giving recoveries in the range of 77.5%-92.0%, and RSDs (n=6) of determined values were ranged from 5.9% to 9.0%.