Determination of glyphosate using off-line ion exchange preconcentration and capillary electrophoresis-laser induced fluorescence detection

An enrichment method for the herbicide glyphosate is presented based on ion exchange solid phase extraction (SPE) technique. A 200-μl micro-pipette tip packed with 50 mg of Bio-Rad AG1-X8 anion exchanger beads was used for offline extraction of glyphosate from 50 ml of spiked river water sample. The retained glyphosate was eluted with 10 mM HCl and then converted quantitatively to the corresponding amine (glycine) using hypochlorite. Subsequent fluorescent labeling using naphthalene-2,3-dicarboxaldehyde (NDA)–cyanide allowed micellar electrokinetic chromatography (MEKC) separation and laser-induced fluorescence detection (LIF) with a violet diode laser. Optimization of the sample clean-up, extraction, elution, conversion and labeling steps enabled analysis of glyphosate in river water in the nanomolar range. Detection limits were 0.04 nM glyphosate in standards and 1.6 nM in spiked river.