Validation of HPLC stability-indicating method for Vitamin C in semisolid pharmaceutical/cosmetic preparations with glutathione and sodium metabisulfite, as antioxidants.

HPLC stability-indicating method was validated for Vitamin C (ascorbic acid) in semisolid pharmaceutical/cosmetic formulations containing glutathione and sodium metabisulfite, as antioxidants. The described procedure included a reliable, precise, accurate and specific method determination employing a 250mm x 4.6mm C(18) column, 0.2% metaphosphoric acid/methanol/acetonitrile (90:8:2, v/v/v) as the mobile phase and detection at 254nm. Nicotinic and ascorbic acids were employed as standards, both presenting purity of 99.0%. Linearity was established for the ascorbic acid concentrations ranging form 1.0 to 12microg mL(-1), accuracy/recovery percentage was 95.46-101.54%, precision values were 0.38 (intra-day) and 1.22% (inter-days), and LOD and LOQ were found to be 0.05 and 0.17microg mL(-1), respectively. The working mobile phase elevated the ascorbic acid retention time to approximately 3.5min at a flow rate of 1.0mL min(-1) and provided resolution of the active from the nicotinic acid (internal standard), degradation product (oxalic acid) and other excipients from the pharmaceutical/cosmetic preparations.