USE OF THE TRIIODIDE-CETYLPYRIDINIUM CHLORIDE MICELLAR SYSTEM FOR THEDETERMINATION OF BENZOYL PEROXIDE IN PHARMACEUTICAL PREPARATIONS

A kinetic spectrophotometric method for the determination of benzoyl p eroxide in acne preparations is proposed. The method is based on the r eduction of benzoyl peroxide by iodide in the cationic micellar medium provided by cetylpyridinium chloride (CPC). The triiodide ion produce d associates with CPC micelles, which gives rise to an absorption maxi mum at 500 nm in addition to substantially increased absorptivity and stability constant far the triiodide complex. Acne preparations can be analyzed directly after dissolution of the samples in ethanol. The de tection limit thus achieved is 0.033 mu g.mL(-1), so the proposed meth od surpasses existing alternative methods insensitivity. The relative standard deviation for 0.25 mu g.mL(-1) is 2.1%.