Thin-Layer Chromatographic Separation of Isomers of Ascorbic Acid and Dehydroascorbic Acid as Sodium Borate Complexes on Silica Gel and Cellulose Plates

A thin-layer chromatography (TLC) method is described for isomers of ascorbic acid (AA) and their oxidation product, dehydroascorbic acid (DHAA), on sodium borate impregnated (B) silica gel and cellulose plates. Borate complexes of AA and DHAA could be separated from each other, with AA migrating further. For comparative purposes, TLC was also attempted using direct (D), reversed-phase (RP), and reversed-phase sodium borate (RP-B) TLC plates with and without metaphosphoric acid (MPA). A reasonable separation of the three AA isomers is achieved on D and RP cellulose plates. Using an RP−silica−MPA plate the three AA isomers as well as the three DHAA isomers are fairly separated from their own group members. The separation of six stereoisomers, three AA isomers, and three DHAA is achieved using a D-cellulose−MPA plate. This procedure has been adopted to separate and identify AA and its oxidation product DHAA in food products, pharmaceutical preparations, and biological tissues and fluids.