Determination of retinol palmitate and tocopherol acetate in lipid microcapsules by HPLC/UV

An original method for the quantitative determination of retinol palmitate (RP) and tocopherol acetate (TA) in lipid microcapsules using reverse-phase high-performance liquid chromatography with ultraviolet detection (HPLC-UV) in isocratic elution mode is proposed. The method includes sample preparation of lipid microcapsules, HPLC separation of microcapsule components TA and RP, as well as metrological support for the quantitative determination of vitamins. Sample preparation of microcapsules included the following stages: dissolution of microcapsules by heating, cooling of the solution, centrifugation and filtration. The proposed sample preparation procedure provides the extraction degree no less than 98.5% for TA and 99.6% for RP, respectively. Optimal HPLC-UV chromatography conditions for isocratic elution were selected. The optimal wavelength of 288 ± 2 nm determined from spectrophotometric measurements provides the joint determination of RP and TA. The effect of mobile phase (MP) composition on chromatographic parameters (retention time, peak area, resolution, peak width, peak asymmetry coefficient) for standard TA and RP samples is considered. The best values for these parameters were determined from the peaks obtained when using the mobile phase acetonitrile: isopropyl alcohol: 1,2-dichloroethane (55:40:5). Calibration dependences of the peak areas on the concentration of TA from 0 to 5% and RP from 0 to 10% were constructed; the correlation coefficients were 0.9981 and 0.9976, respectively. The accuracy of the method for the quantitative determination of fat-soluble vitamins (TA and RP) in lipid microcapsules was assessed in spike recovery tests. The method can be recommended for quality control laboratories to determine the quantitative content of fat-soluble vitamins such as retinol palmitate and tocopherol acetate in the pharmaceutical, cosmetic and food industries.