2023 Volume 72 Issue 4.5 Pages 183-190
This paper describes the development of a fast HPLC assay method of L-ascorbic acid employing HILIC mode and its application to the evaluation of photostability of unpacked pharmaceuticals and soft drinks containing L-ascorbic acid. Among four different types of HILIC columns, specifically amide type, diol type, pentahydroxy (5OH) type, and cyclodextrin type, of which most were core-shell type columns, a core-shell type 5OH column was selected after the optimization of the analytical conditions. With the mobile phase of 0.05 mol L−1 ammonium formate and acetonitrile (25 : 75), three ascorbic acid analogues, isoascorbic acid (erythorbic acid), L-ascorbic acid and L-ascorbic acid 2-glucoside, were completely separated within 3 min in that order. The developed HILIC-HPLC L-ascorbic acid assay method using L-ascorbic acid 2-glucoside as an internal standard substance was applied to the photostability of pharmaceuticals once opened from the final packaging, such as a PTP sheet, and soft drinks with bottle caps removed. Photoirradiation was carried out in a light cabinet with a black light lamp with abundant wavelength of 365 nm. After 20 days irradiation, L-ascorbic acid content in the formulations was determined by the developed HPLC method and residual rates were compared with those not subjected to light irradiation (control samples). Among four dosage forms, namely tablets, granules, powders, and injections, some decrease was observed in the powders. For soft drinks, after removing the caps and irradiating with UV light for 2 days, the content of L-ascorbic acid decreased considerably and its rate correlated with the concentration of L-ascorbic acid. The lower concentration of L-ascorbic acid, the higher photodegradation of L-ascorbic acid. In soft drinks, even when stored in a refrigerator for a few days, the degradation of L-ascorbic acid was observed after opening.
