Absolute determination method for trace quantities of enantiomer of glufosinate by γ-cyclodextrin modified capillary zone electrophoresis combined with solid-phase extraction and on-capillary concentration

A highly sensitive and accurate determination method for trace quantities of enantiomers of glufosinate (D,L-GLUF), a phosphorus-containing amino acid-type herbicide, has been studied. The present method is based on the change in the mole ratio of the enantiomeric isomers after spiking of a known amount of an isomer (L-GLUF). The chiral separation and detection were made by gamma-cyclodextrin modified capillary zone electrophoresis (gamma-CD-CZE) with fluorescence detection. Solid-phase extraction Of D,L-GLUF with titania was investigated as the pre-separation method to eliminate coexisting materials such as inorganic salts and organic compounds in river water. A separated D,L-GLUF was labeled with dansyl chloride and subjected to the on-capillary concentration using large-volume sample stacking (LVSS) before gamma-CD-CZE. The detection limit of the present method was as low as 2.0 x 10(-9) M. The present method was successfully applied to a model sample containing 2.0 x 10(-7) M D,L-GLUF in river water. It was confirmed that trace quantities Of D- and L-GLUF in environmental samples can be accurately determined without any calibration curves and comparison standards.