Rapid method for the determination of eight chlorophenoxy acid residues in environmental water samples using off-line solid-phase extraction and on-line selective precolumn switching

Abstract

A rapid procedure for the determination of eight chlorophenoxy acid herbicides in environmental water samples is described. The method involves two off-line solid-phase extraction (SPE) procedures prior to analysis by liquid chromatography with (pre)column switching and UV detection at 228 nm. SPE sample pretreatment consists in loading a 50-ml sample on a 100-mg C 18 cartridge followed by clean-up of the extract on a 100-mg silica cartridge. The extracts obtained by this procedure are analysed with coupled column liquid chromatography (LC) using a precolumn packed with internal surface reversed-phase material (5-μm GFF II) and an analytical column packed with C 18 material (3-μm Microspher). The separation of the extracts from the SPE procedure takes less than 15 min, rendering an overall procedure with a throughout of 40 samples per day. The chlorophenoxy acids 2,4-D, MCPA, 2,4-DP, MCPP, 2,4,5-T, 2,4-DB, MCPB and 2,4,5-TP can be assayed in the various water samples down to a level of 0.1 μg l −1. Drinking, ground and surface water samples spiked at levels of 0.5 and 2.0 μg l −1 yielded average recoveries between 80 and 110% ( n=5 for each sample type and spiked level)_with relative standard deviations between 1 and 10%. The calibration graphs are linear over at least three orders of magnitude.