Synergistic effect of field enhanced sample injection on micelle to solvent stacking in capillary electrophoresis

Injection of a sodium dodecyl sulfate micellar plug prior to the sample solution induced transient micellar phase extraction of cationic drugs in capillary electrophoresis. Micelle to solvent stacking mechanism was utilized by preparing the sample in aqueous organic solvent. Synergism was achieved with field enhanced sample injection that allowed larger sample loads. Micelle to solvent stacking occurred concurrently with the enhanced injection after the fast moving analytes electrophoretically migrated into the micellar plug. This was different from stacking combinations with field enhancement where the electric field strength difference was involved in analyte focusing. Using a sample diluent that had one-tenth the conductivity of the background solution, the strategy afforded thousands-fold improvements in peak height and LODs (S/N = 3) of as low as 1.1 ng/mL. The results were repeatable and linear. Adaptability to real sample analysis was evaluated using spiked urine sample after minimal sample clean-up.