Stability of Retinol Analogs. IX. Stability of Vitamin A Acetate in Aqueous Ethanolic Solutions and Quantitative Analysis of Its Decomposition Products by High Performance Liquid Chromatography

The stability of vitamin A (VA) acetate in ethanolic solutions with various water contents and the formation and disappearance of its major decomposition products were studied quantitatively by high performance liquid chromatography (HPLC) using Li-Chrosorb Alox T (basic alumina). Three major decomposition products were fractionated by HPLC and identified as anhydro VA, 4-ethoxy anhydro VA, and VA ethyl ether. VA ethyl ether has an ultraviolet (UV) spectrum similar to that of VA acetate and caused interference with the estimation of VA acetate in these test solutions by UV spectrophotometry. The structure of 4-ethoxy anhydro VA, which has a UV spectrum similar to that of the retro VA analog, was assigned by mass spectroscopy, nuclear magnetic resonance, UV, and infrared analyses. This substance was largely converted into anhydro VA in aqueous ethanolic solution and is thus considered to be a precursor of anhydro VA.