Electrically driven microseparation methods for pesticides and metabolites: I. Micellar electrokinetic capillary chromatography of carbamate insecticides with MEGA-borate and SDS surfactants

The migration behavior of some representative carbamate insecticides in mic ellar electrokinetic capillary chromatography (MECC) was investigated over a wide range of elution conditions, including the nature and concentration of the surfactant and the concentration of added urea in the running electr olyte. Decanoyl-N-methylglucamide (MEGA 10) surfactant was compared with th e traditionally used sodium dodecyl sulfate (SDS) surfactant for separation of the carbamate insecticides under investigation. The MEGA 10 micellar sy stem is based on the complexation of MEGA 10 with berate, yielding an in si tu charged micelle (i.e., MEGA 10-borate micelle), whose surface charge den sity can be readily manipulated by varying the pH and the concentrations of berate and MEGA 10 in the running electrolyte. This flexibility, in turn, allowed the modulation of the migration time window and, consequently, the analysis time. Because of its relatively weaker hydrophobic character, the MEGA 10-borate micellar system permitted the resolution of 9 different carb amate insecticides in about 12 min. Conversely, with the SDS micellar syste m, whose hydrophobicity is higher, the separation of all 9 solutes necessit ated the addition of 4.0M urea, a condition that brought about a doubling o f the analysis time. In addition, the MEGA IO-borate micellar system produc ed twice as many plates per min as did the SDS micellar system. Because MEG A 10-borate yielded results superior to those of the SDS micellar system, o n-column preconcentration of the carbamate insecticides was attempted in ME GA 10-borate by using the concept of field-amplified sample stacking (FASS) . Thus far, only a few attempts have been made toward the application of FA SS in MECC of neutral compounds such as carbamate insecticides.