Effect of drying on the degradation of cationic surfactants and separation performance in capillary zone electrophoresis of inorganic anions

Tetradecyltrimethylammonium bromide (TTAB) is used in capillary zone electrophoresis (CZE) to control the direction and magnitude of the electroosmotic flow and the migration time of analyte anions. Drying of the hygroscopic TTAB at 100°C overnight has been found to influence the final CZE separation by providing improved resolution, precision of migration times, and enhanced detection response for hydrogenphosphate. Chemical analysis of the dried TTAB using IR and GC–MS indicated the presence of small amounts of an unexpected tertiary alkylamine, tetradecyldimethylamine. This amine appears to contribute to the improved separation, probably by making more effective the masking of silanophilic activity at the capillary surface and/or generating a more stable double-layer.