Rapid determination of glufosinate in environmental water samples using 9-fluorenylmethoxycarbonyl precolumn derivatization, large-volume injection and coupled-column liquid chromatography

Abstract

The application of 9-fluorenylmethoxycarbonyl (FMOC) derivatization prior to coupled-column LC with fluorescence detection using a reversed-phase C 18 column (C-1) coupled to an ion-exchange column (C-2) proved to be useful for the rapid determination of the very polar pesticide glufosinate in a variety of environmental water samples at the sub-ppb level. The separation power of the first column is used to provide (i) sensitivity by means of large-volume injection and (ii) selectivity by an efficient preseparation of the very polar analyte from the less polar interferences including the excess of unreacted FMOC reagent. Conditions for the important parameters with respect to separation and sensitivity, viz., sample injection volume, separation power of the columns and composition of the buffer and modifier in the mobile phases, were established, resulting in a method with which glufosinate in water samples, after FMOC derivatization, can be assayed at a level of 0.25 μg/l (signal-to-noise ratio = 3) in less than 15 min. The overall procedure has a sample throughput of more than 50 per day. Drinking, ground and surface water samples spiked at levels between 0.5 and 5.0 μg/l yielded average recoveries between 90 and 105% ( n = 5 for each sample type and spiked level) with relative standard deviations between 1 and 5%. The method is linear over at least three orders of magnitude ( r > 0.999). The limit of detection can be lowered to 0.1 μg/l by means of a simple preconcentration step with a Rotavapor.