The challenge of detecting the herbicide glyphosate and its metabolite AMPA in seawater - Method development and application in the Baltic Sea.

The globally used herbicide glyphosate and its metabolite aminomethylphosphonic acid (AMPA) have not yet been reported to occur in the marine environment, presumably due to a lack of suitable analytical methods. In this study, we developed two new methods for the analysis of glyphosate and AMPA in seawater: a small-scale method, which includes an SPE cleanup step that minimizes salt-matrix effects during LC-MS/MS analysis, and a large-scale method that employs an additional SPE preconcentration step. Different SPE materials were evaluated for their suitability to enrich glyphosate and AMPA from saltwater and a molecularly imprinted polymer was selected. Both methods were validated in ultrapure water and environmental seawater. Achieved limits of detection with the small-scale method were 6 and 8 ng/L for glyphosate and AMPA, while the large-scale method achieved 0.12 and 0.22 ng/L, respectively. The small-scale method was used to analyze environmental samples from the Warnow Estuary in Germany. Glyphosate and AMPA could be successfully detected in the samples, but could not be measured beyond the saline estuary due to dilution and degradation effects. A set of samples from the western Baltic Sea was analyzed with the large-scale method. Glyphosate and AMPA could be detected in all Baltic Sea samples, especially at stations close to estuaries. To the best of our knowledge, this is the first report on the occurrence of glyphosate and AMPA in seawater.