3.3. Specificity
The specificity of the HPLC stability-indicating method for
ascorbic acid quantitation in pharmaceutical/cosmetic preparations
was investigated in order to obtain an indication of the
possible interferents from excipients of the topical preparations,
the nicotinic acid and the degradation product of the active substance,
the oxalic acid.
The presence of the excipients of the o/w emulsion and
aqueous gel (Fig. 2), including the antioxidants glutathione and
sodium metabisulfite, and the oxalic acid did not cause any interference
with the ascorbic acid peak. Under these conditions,
ascorbic acid was observed to be well resolved from components
of formulations and the potential degradation product of
the Vitamin C.