Simultaneous determination of azelaic and benzoic acids in topical preparations by liquid chromatography

Summary An isocratic, reversed-phase liquid chromatographic (LC) method has been developed for the simultaneous determination of azelaic and benzoic acids in pharmaceutical creams. The compounds were separated on a C₁₈ column (4 μm particles); the mobile phase was methanolwater, 40∶60, containing 10mm ammonium acetate and with the pH adjusted to 5.0. Detection was performed at 220 nm. The method was validated for accuracy, linearity, precision, and selectivity. Recoveries at levels corresponding to 80% to 120% of the declared content of the creams ranged from 99.5 to 101.8% and from 100.4 to 102.1% for azelaic and benzoic acids, respectively. The calibration graphs were linear in the ranges 20–1400 μg mL⁻¹ for azelaic acid (correlation coefficient,r ₁>0.99999), and 0.1–7.0 μg mL⁻¹ for benzoic acid (r>0.99998).