Rapid determination of glyphosate, aminomethyl phosphonic acid, glufosinate, and ethephon residues in environmental water by direct injection-ultra performance liquid chromatography-triple quadrupole mass spectrometry

Abstract

A simple method based on direct injection-ultra performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-MS/MS) was established for the rapid determination of glyphosate, aminomethyl phosphonic acid, glufosinate, and ethephon residues in environmental water. The water samples were filtered through a 0.22-μm filter membrane or frozen and centrifuged to remove impurities, and then, the filtrate was directly subjected to quantitative analysis without derivatization. The analytes were separated on a Metrosep A Supp 5 column (150 mm×4.0 mm, 5 μm), and gradient elution was carried out using an ammonium bicarbonate-ammonia solution as the mobile phase. The data were collected by positive electrospray ionization in the multiple reaction monitoring (MRM) mode. The results showed that the correlation coefficients (r) of the linear calibration curves were greater than 0.999 in the corresponding linear ranges (0.50-50.0 μg/L). The detection limits of the analytes were 0.05-0.09 μg/L. The recoveries of glyphosate, aminomethyl phosphonic acid, glufosinate, and ethephon were in the ranges 76.3%-108%, 83.0%-107%, and 87.0%-105% at low, medium, and high spiked levels, respectively. The corresponding relative standard deviations were in the ranges 2.0%-12.3%, 2.4%-5.6%, and 2.7%-6.8%. Using this method, 34 water samples collected from Hainan Province were analyzed, among which 30 drinking water sources were found to be free from the four pesticides. Glyphosate and aminomethyl phosphonic acid were detected in three water samples near a betel nut orchard, while glufosinate and aminomethyl phosphonic acid were detected in a water sample near a banana orchard. This method is advantageous over the traditional derivatization method because of its simple operation, good reproducibility, and high accuracy; furthermore, the matrix interference effect is absent. Thus, this method is suitable for analyzing glyphosate, aminomethyl phosphonic acid, glufosinate, and ethephon residues in environmental water samples.