Determination of Retinyl Palmitate and Tocopheryl Acetate in Lipid Microcapsules by High-Performance Liquid Chromatography with Ultraviolet Detection

The article presents a procedure for sample preparation and determination of tocopheryl acetate (TA) and retinyl palmitate (RP) in lipid microcapsules by reversed-phase high-performance liquid chromatography with ultraviolet detection (HPLC-UV) in isocratic elution mode. The procedure includes dissolution of microcapsules under heating, cooling of the solution, centrifugation, filtration, and chromatographic separation under chosen conditions. The optimum detection wavelength of 288 ± 2 nm is determined based on spectrophotometric measurements which makes it possible to execute joint determination of RP and TA. The effect of the composition of a mobile phase (MP) on chromatographic parameters (retention time, peak area, resolution, peak width, peak asymmetry coefficient) for standard samples of TA and RP is considered: the best values of the specified parameters are provided by the use of an acetonitrile–isopropyl alcohol–1,2-dichloroethane mobile phase at a volume ratio of 55 : 40 : 5. The proposed procedure makes it possible to determine TA in a range of concentrations of 0 to 5%, and RP, of 0 to 10%. The accuracy of the results of determining fat-soluble vitamins (TA, RP) in lipid microcapsules is confirmed by the spike-recovery method. The proposed sample preparation procedure provides the degree of extraction of no less than 98.5% for TA and no less than 99.6% for RP. The procedure can be recommended for determining fat-soluble vitamins at quality control laboratories in the pharmaceutical, cosmetic, and food industries.