Moisture induced solid phase degradation of L-ascorbic acid - part 2, separation and characterization of the major degradation products

The influence of moisture in the presence and absence of air on the solid s tate degradation of L-ascorbic acid has been investigated previously [1]. R eaction kinetics were studied using tristimulus colorimetry and a quantitat ive high performance liquid chromatographic assay for both total L-ascorbic acid and dehydroascorbic acid. The degradation gave rise to a discolourati on of the samples, the most severely degraded samples were almost black in appearance although over 68% w/w of the L-ascorbic acid remained. The sampl es were analyzed for the presence of carbonyl compounds, furan related comp ounds, compounds responsible for the discolouration and evolution of carbon dioxide. No 2,4-dinitrophenylhydrazine (2,4-DNP) derivatives of carbonyl c ompounds or furan related compounds were detected by HPLC. An HPLC screenin g procedure was developed which was used to monitor for compounds responsib le for the discolouration, at least eight unknown compounds were resolved a nd a relative response factor of 5.47 was assigned to them with respect to L-ascorbic acid at 280 nm. One mole of carbon dioxide was evolved per mole of L-ascorbic acid. This paper describes the investigation into the identit y of the degradation products. (C) 1999 Elsevier Science B.V. All rights re served.