A Newly Developed Approach for Analyzing the Degradation of Glyphosate and Aminomethylphosphonic Acid in Different Salinity Levels

The report for the global presence of herbicide glyphosate and its metabolite aminomethylphosphonic acid (AMPA) is presently limited in the marine environment, presumably due to a lack of analytical methods capable of detecting these compounds at low concentrations in high-salinity matrices. In the present study, we aimed to develop a time-saving and reliable method for the analysis of glyphosate and AMPA in different salinity levels of seawater. This novel method integrates a derivatization process with a solid-phase extraction cleanup step to mitigate salt-matrix effects during high-performance liquid chromatography coupled with tandem mass spectrometry analysis. The present method was validated in environmental freshwater and seawater with the limit of quantitation of 2 and 0.5 ng/mL and coefficient of variation percentage of 0.63–3.15% and 0.59–3.07% for glyphosate and AMPA, respectively. The degradations of three concentrations of spiked glyphosate (10, 100, 1000 mg/L) were assessed under two treatment conditions: with and without sterilization and at three salinity levels (0, 17.5, 35‰) over a period of 112 days. The results show that glyphosate degradation is significantly higher in non-sterilized water compared to sterilized conditions, indicating that microbial activity is the primary driver of degradation. Furthermore, brackish water appears to provide a more favorable environment for the microbial biodegradation of glyphosate.