Nonderivatization method for determination of highly polar pesticides and their metabolites in environmental water by ultra-high performance liquid chromatography-tandem mass spectrometry

A simple, direct injection and non-derivatized analytical method was developed for rapid determination of six highly polar compounds, including ethephon, glyphosate, glufosinate, aminomethylphosphonic acid, 3-methylphosphinicopropionic acid, and glufosinate-N-acetyl in environmental water by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The environmental water samples were centrifuged and filtered through 0.22 µm filter membrane to remove solids and were directly injected for quantitative analysis without derivatization. The target compounds were separated by Waters Acquity UPLC HSS T3 column (100 mm × 2.1 mm, 1.8 µm). Chromatographic separation was carried out by gradient elution with mobile phase A (water with 0.1% formic acid and 5 µmol/L medronic acid) and mobile phase B (methanol). The target compounds were finally detected using electrospray ionization and multiple reaction monitoring mode (MRM). Quantitative analysis was performed using the external standard calibration curves. The results showed that all six compounds had good linear relationship within their respective linear ranges, and the coefficient of determination (R²) were higher than 0.99. The average recoveries of six compounds in water samples were from 75% to 100% at spiked levels ranging from 10 µg/L to 200 µg/L. The intra-day and inter-day relative standard deviations(n=6) were 3.6%-7.0% and 4.3%-7.5%, respectively. The limits of quantification (LOQ) were 0.5-10 µg/L. Ten surface water samples collected from three areas were detected using the established method, and the results showed that the six compounds were all not detected. Compared with other derivatization methods, this method has the advantages of simplicity, rapidity, good reproducibility, and high sensitivity, and it may provide reference for the detection of highly polar compounds such as ethephon, glyphosate, glufosinate, and their metabolites in environmental water.