Micro-scale membrane extraction of glyphosate and aminomethylphosphonic acid in water followed by high-performance liquid chromatography and post-column derivatization with fluorescence detector

A carrier-mediated supported liquid membrane micro-extraction using single hollow fiber membrane suitable for the determination of the herbicide glyphosate and its main metabolite aminomethylphosphonic acid in water is reported. A solution of 0.20M Aliquat-336, a cationic carrier, in di-n-hexyl ether was selected as the supported liquid. A 20 mu L of 1.0 M potassium chloride as the acceptor phase was filled in the membrane lumen. The membrane was immersed in a 20 mL of pH 9.0 sample solution. After 60-min extraction, the acceptor phase was analyzed by high-performance liquid chromatography with post-column derivatization. The enrichment factors were found to be 853 and 136 for glyphosate and aminomethylphosphonic acid, respectively. The method detection limits are 0.22 mu g/L for glyphosate and 3.40 mu g/L for aminomethylphosphonic acid. The procedure was validated and showed good accuracy and precision over a large linear dynamic range. The validated method was tested for the analysis of both analytes in spiked groundwater with good success. (C) 2008 Elsevier B.V. All rights reserved.