ANALYSIS AND DEGRADATION STUDY OF GLYPHOSATE AND OF AMINOMETHYLPHOSPHONIC ACID IN NATURAL-WATERS BY MEANS OF POLYMERIC AND ION-EXCHANGE SOLID-PHASE EXTRACTION COLUMNS FOLLOWED BY ION CHROMATOGRAPHY POSTCOLUMN DERIVATIZATION WITH FLUORESCENCE DETECTION

The quantitative trace determination of glyphosate and its major metab olite, aminophosphonic acid (AMPA) in natural waters was achieved by m eans of ion-exchange chromatography. Fifty mi of natural water sample was preconcentrated by a two-step procedure: first the sample was perc olated through a polymeric cartridge, LiChrolut EN, then through an an ion-exchange column mechanism, and finally analyzed by ion-exchange ch romatography followed by post-column reaction coupled to a fluorimetri c detector. Linear calibration graphs were obtained between 5 and 200 mu g l(-1). Limits of detection ranged from 2 mu g l(-1) of glyphosate and 4 mu g l(-1) of AMPA. A study of the degradation of glyphosate in environmental waters under characteristic conditions was carried out to figure out the main degradation pathways of this compound. Half-liv es of glyphosate varied from 60 h for ground water samples exposed to sunlight to 770 h for those stored under dark conditions. (C) 1998 Els evier Science B.V. Ail rights reserved.