title: Analysis of vitamin formulations by electrokinetic chromatography utilizing tetradecylammonium ions as the pseudostationary phase.
abstract: A recently proposed method for the separation of fat-soluble vitamins by electrokinetic chromatography was further developed and investigated in the present study. The separation medium consisted of acetonitrile-water (80:20 v/v) and contained 80 mM tetradecylammonium bromide (TDA+); the content of acetonitrile served to maintain the hydrophobic vitamins dissolved during electrophoresis, while the TDA+ ions served as the pseudostationary phase. With the cathode placed at the outlet of the capillary, the fat-soluble vitamins were separated based on different hydrophobic interactions to the TDA+ ions and migrated in order of decreasing hydrophobicity prior to the electroosmotic flow. Migration time stability was significantly enhanced by the addition of 4 mM borate to the separation medium. The separation system was validated for the determination of vitamin E acetate in commercial tablets; quantitative results deviated by less than 3.5% from specified values, varying by less than 2.5% relative standard deviation (RSD) for within-day experiments, and by less than 6.5% RSD during between-day experiments. The separation system was compatible with injection solvents ranging in polarity from water to tetrahydrofuran, and was even capable of separating the water-soluble vitamins B1, B2, B12, and nicotinamide.
authors.affiliation: School of Pharmacy, University of Oslo, Norway.
authors.forename: O
authors.initials: O
authors.lastname: Naess
authors.forename: T
authors.initials: T
authors.lastname: Tilander
authors.forename: S
authors.initials: S
authors.lastname: Pedersen-Bjergaard
authors.forename: K E
authors.initials: KE
authors.lastname: Rasmussen
mesh_terms: D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D019075:Electrophoresis, Capillary / Q000379:methods*; D000644:Quaternary Ammonium Compounds; D014815:Vitamins / Q000302:isolation & purification*
chemical_list: D000644:Quaternary Ammonium Compounds; D014815:Vitamins