Separation of δ-, γ- and α-tocopherols by CEC

Abstract

In this study capillary electrochromatography (CEC) was used for the separation of three tocopherols (TOHs), namely δ-, γ- and α-TOH and the antioxidant compound, butylated hydroxytoluene (BHT). The CEC experiments were carried out using an octadecylsilica (ODS) stationary phase packed, in our laboratory, in a fused-silica capillary (100 μm I.D., 365 μm O.D.×33 cm of total length and 24.6 or 8.4 cm effective length). The mobile phase was composed by a mixture of methanol (MeOH) and acetonitrile (ACN), at different concentrations and 0.01% (w/v) of ammonium acetate. Retention time ( t R), retention factor ( k), resolution ( R s) of the three TOHs were strongly influenced by the organic solvent composition of the run buffer and by the effective length of the capillary. Optimum experimental conditions were found even employing the short effective length of the capillary achieving the baseline separation of the studied analytes in a relatively short time (less than 5 min). The optimized method was applied to the qualitative analysis of vitamin E (α-TOH) present in a human serum extract.