Automated trace level determination of glyphosate and aminomethyl phosphonic acid in water by on-line anion-exchange solid-phase extraction followed by cation-exchange liquid chromatography and post-column derivatization

An automated method based on the on-line coupling of anion-exchange solid-p hase extraction (SPE) and cation-exchange liquid chromatography followed by post-column derivatization and fluorescence detection has been developed f or the trace level determination of glyphosate and its primary conversion p roduct aminomethyl phosphonic acid (AMPA) in water. PRP-X100 poly(styrene-d ivinylbenzene)-trimethylammonium anion-exchange cartridges (20X2 mm, 10 mum ) were selected for the SPE of glyphosate and AMPA. The ionic compounds pre sent in the samples strongly influenced the extraction of both analytes; ho wever, when an on-line ion-exchange clean-up step was introduced before sam ple SPE, the problem was largely solved. By processing 100-ml samples detec tion limits better than 0.02 mug/l for glyphosate and 0.1 mug/l for AMPA we re achieved in river water. Both analytes were unstable in solution and the approach of storing samples on the PRP-X100 SPE cartridges was evaluated f or a period of I month under three different storage conditions (deep freez e, refrigeration and 20 degreesC). (C) 2001 Published by Elsevier Science B .V.