3.2. Linearity
The linearity was studied over a concentration range of
1.0–12.0gmL−1. To evaluate the influence of excipients from
topical formulations, linearity was also studied with the presence
of the o/w emulsion and aqueous gel analyte-free and no
interference was found, maintaining the linear and proportional
relationship. Replicates of three injections were performed for
each sample.
A standard curve was constructed according to the ratio
peaks of ascorbic acid/nicotinic acid versus peaks for ascorbic
acid concentrations. The results demonstrated satisfactory and
consistent behavior of the HPLC stability-indicating method.