Development of a flotation-spectrophotometric method for determination of cetylpyridinium chloride in pharmaceutical products

Abstract

Recebido em 17/8/10; aceito em 16/11/10; publicado na web em 18/2/11A new simple and sensitive flotation-spectrophotometric method for the determination of cetylpyridinium chloride (CPC) is reported. The method is based on the formation of an ion-associate between CPC and Orange II (OR) which is floated in the interface of aqueous phase and n-hexane by vigorous shaking. The aqueous solution was discarded and the adsorbed ion associate on to the wall of a separating funnel was dissolved in a small volume of methanol solvent and its absorbance was measured at 480 nm. The apparent molar absorptivity (ε) of the ion associate was determined to be 4.12 x 10 5 L mol -1 cm -1 . The calibration graph was linear in the concentration range of 15-800 ng mL -1 of CPC with a correlation coefficient of 0.9988. The limit of detection (LOD) was 10.8 ng mL -1 . The relative standard deviation (RSD) for determination of 100 and 800 ng mL -1 of CPC was 3.47 and 2.04% (n=7), respectively. The method was successfully applied to the determination of CPC in a commercial mouth washer product.