A rapid method was developed whereby vitamins A, D (ergocalciferol), and E in multivitamin products are measured in a common assay sample. The method depends on reversed-phase partition chromatography by which the vitamin alcohols are eluted in separate fractions from a column. Vitamins A and E are then determined by their UV absorption, while vitamin D is measured colorimetrically with an antimony trichloride reagent. The column consists of diatomaceous earth impregnated with dimethyl polysiloxane, with n-heptane as the immobile solvent, and 90% methanol followed by 95% methanol as the mobile solvents. Vitamins A and D elute in that order in the 90% methanol, and finally vitamin E elutes in the 95% methanol fraction. The method is widely applicable to various types of multivitamin and vitamin-mineral products including oil-based, water-based, and dry formulations.
Keyphrases 0 Vitamins-combined analyses, vitamins A, D (ergocalciferol), and E in multivitamin preparations, reversed-phase partition chromatography 0 Chromatography, reversed-phase partition-combined analyses, vitamins A, D, and E in multivitamin preparations Multivitamin preparations-combined analyses, vitamins A, D, and E, reversed-phase partition chromatography Tube was similar to that used in the second column chromatography in Buchler model PTFE-1G. Cary model 15, equipped with 0-1 absorbance slide wire. the USP vitamin D assay (1) but with a larger diameter bottom section. 4 Purified by filtration through aluminum oxide, Brockmann activity grade I, basic, for chromatography (J. T. Baker Chemical Co., Phillipsburg, N.J.), using 110 g/3.79 liters (1 gallon) of benzene and 220 g/3.79 liters (1 gallon) of ethylene dichloride in a 3.9-cm i.d. tube and 40 g/lOOO ml of antimony trichloride in purified ethylene dichloride in a 2.5-cm i.d. tube. Kept in ori inal metal containers for satisfactory storage.