Twenty microlitres of the above mentioned solution were analysed by RP-HPLC, which consisted on a binary LC pump model Prostar 250, an UV/Vis detector and an autosampler. The chromatographic column was a Novapak C18 (250 mm 4.6 mm i.d; 4 lm) from Waters thermostated at 25 C. Ascorbic acid was released under isocratic conditions using bi-distilled de-ionised water acidified with sulphuric acid to pH 2.2 as solvent at a flow rate of 0.6 ml/min.