Simultaneous determination of all-trans-retinoic acid, beta-carotene, and vitamin A in galenic preparations by liquid chromatography.
The concentrations of vitamin A, beta-carotene, and all-trans-retinoic acid in oral preparations were determined in a single analysis by a method based on isocratic, reversed-phase liquid chromatography (LC). The LC system consisted of a C18 column, a mobile phase of acetonitrile, dichloromethane, methanol, and water and a UV detector set at 330 nm. The linearity ranges were 25-250 ng/mL for trans-retinoic acid and vitamin A, and 100-1,000 ng/mL for beta-carotene. This LC method for the determination of retinoids is simple, precise, and accurate. No extraction procedure is required before the chromatographic analysis; only a suitable dilution is necessary. The method proved to be reliable, fast, and economical. Furthermore, this method is indicative of stability, because it allows for the determination of degradation products such as 13-cis-retinoic acid.