Determination of glyphosate and aminomethylphosphonic acid in rice using hydrophilic interaction chromatography-tandem mass spectrometry

A method was developed for the simultaneous determination of glyphosate (Gly) and aminomethylphosphonic acid (AMPA) residues in rice using hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS). The samples were extracted with water, and purified using a C18 solid phase extraction cartridge followed by an ultrafiltration membrane to remove interfering materials. Gly and AMPA were separated on an HILIC column with the mobile phases of 1 mmol/L ammonium acetate (pH 11.0 adjusted with ammonium hydroxide) and acetonitrile, and finally detected with negative electrospray ionization (ESI-) in multiple reaction monitoring (MRM) mode. The matrix-matched external standard calibration curves were used for quantitative analysis. The sample pretreatment of Gly and its metabolite was successfully carried out without any derivatization. Under the optimal analytical conditions, the linearities of Gly and AMPA were in the concentration ranges of 0. 001 to 0. 250 mg/L and 0. 002 5 to 0. 250 mg/L respectively, with the correlation coefficients of 0. 999 5 for the both analytes. The limits of detection (S/N = 3) of the method were 0.010 mg/kg for Gly, and 0.020 mg/kg for AMPA. For all the samples, the mean spiked recoveries of Gly and AMPA were in the range from 96.3% to 107.3% at 3 spiked levels (0.100, 0.500 and 2.500 mg/kg), and the relative standard deviations (RSDs, n = 3) were in the range of 1.3%-9.1%. The method is easy, fast, sensitive and accurate, and can meet the requirements of the determination of Gly and AMPA pesticide residues in rice.