Enrichment and low‐level determination of glyphosate,aminomethylphosphonic acid and glufosinate in drinking water after cleanup by cation exchange resin

For the determination of glyphosate, aminomethylphosphonic acid and glufosinate in drinking water, different procedures of enrichment and cleanup were examined using anion exchange or SPE. In many cases interactions of, e.g. alkaline earth metal ions especially calcium could be observed during enrichment and cleanup resulting in loss of analytes. For that reason, a novel cleanup and enrichment procedure for the determination of these phosphonic acid herbicides has been developed in drinking water using cation‐exchange resin. In summary, the cleanup procedure with cation‐exchange resin developed in this study avoids interactions as described above and is applicable to calcium‐rich drinking water samples. After derivatization with 9‐fluorenylmethylchloroformate followed by LC with fluorescence detection, LOD of 12, 14 and 12 ng/L and mean recoveries from real‐world drinking water samples of 98±9, 100±16 and 101±11% were obtained for glyphosate, aminomethylphosphonic acid and glufosinate, respectively. The low LODs and the high precision permit the analysis of these phosphonic acid herbicides according to the guidelines of the European Commission.