Determination of potential content of vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) in gelatin-coated beadlets, oil-based mixtures, and multivitamin tablet and capsule formulations.

A high-performance liquid chromatographic procedure was used to determine routinely the potential vitamin D content in raw materials and multivitamin formulations. The method employs a microparticulate silica column to separate vitamin D from its degradation products as well as other fat-soluble vitamins. Sample preparation is simple, and the chromatographic time is less than 20 min when progesterone is added to the injection mixture as an internal standard. Replicate analyses of complex multivitamin formulations demonstrate precision with a relative standard deviation of less than 4%. Spiked placebos typically show 98--100% recovery and a linear chromatographic response. The use of bulk drug as a working reference standard is recommended for the determination of the potential vitamin D concentration in pharmaceutical multivitamin preparations.