EVALUATION OF DEACTIVATED REVERSED PHASES FOR THE ANALYSIS OF AN N,N,N-TRIMETHYLETHANAMINIUM ANALOG OF ALPHA-TOCOPHEROL - APPLICATION TO ITS PURITY CONTROL AND DETERMINATION IN BIOLOGICAL SAMPLES

Several non-deactivated and deactivated reversed-phase columns were evaluated for the determination of the quaternary ammonium analogue of a-tocopherol, 3,4-dihydro-6-hydroxy-N,N,N,2,5,7,8-heptamethyl-2H-1-benzopyran-2-ethanaminium 4-methylbenzenesulphonate, which is being developed as a cardioselective antioxidant. The retention characteristics of the compound, its corresponding quinone and their tertiary amine analogues were studied using UV detection at 280 nm. The effect of pH, ionic strength of the sodium phosphate buffer and nature of the organic solvent (methanol, acetonitrile) on the retention times and peak symmetry of the different compounds studied was evaluated. The effect of the addition of a basic modifier, N,N-dimethyloctylamine, was also investigated. The best results were obtained with deactivated C-8 and C18 phases and with a mixture of methanol and sodium phosphate buffer. The method was applied to the purity control of the title compound and is compatible with electrochemical detection, which allows the determination of this a-tocopherol analogue and its corresponding amine in the sub-picomolar range.