Moisture induced solid phase degradation of L-ascorbic acid - part 3, structural characterisation of the degradation products

The influence of moisture on the solid phase degradation of L-ascorbic acid and the chemical characteristics of the degradation products have been inv estigated previously [Shephard et al. (1998) (in press)]. Moisture induced degradation in the solid phase leads to severe discolouration. This paper d escribes the isolation of the compounds responsible for the discolouration and their partial chemical identification. Eight different degradation comp ounds were found to be present in a severely discoloured sample [Shepherd e t al. (1998) (in press)]. Three of the compounds were present at levels abo ve 1% of the total chromatography peak area with the major degradation peak present at 29% in a sample with 5% v/w moisture present when stored at 60 degrees C for 42 days. The major impurity was isolated and was found to exh ibit a lambda(max) at 280 nm with further absorbance to 600 nm. This materi al was pyrolysed at 300, 500, and 600 degrees C. Amongst the volatile pyrol ysates tentatively identified were furfural, 2-furancarboxylic acid, 1-(2-f uranyl)-ethanone, tetrahydrofuran and 1-(2-furanyl)1-propanone along with s ome aromatic compounds such as benzene and phenol. The periodate consumptio n of the major impurity was examined and the products of the reaction inves tigated. Estimation of hydroxyl and carbonyl group content by acetyl group determination of the acetate and reduced acetate showed that for every five repeating units there was one hydroxyl group and for every four repeating units there was one carbonyl group. Elemental analysis gave 46.26% carbon, 5.42% hydrogen and 48.32% oxygen giving an empirical formula of CH2O. (C) 1 999 Elsevier Science B.V. All rights reserved.