Spectrophotometric Determination of Bismuth with Alizarine Red S and Cetylpyridinium Chloride - Application to Water Samples, Urine and Veterinary Preparation

A simple, accurate, sensitive and reliable method for spectrophotometric determination of Bismuth(III) is developed. The method is based on the reaction of bismuth (III) with alizarin red S (ARS) and cetylpyridinium chloride (CPC) in the presence of Triton X-100 at pH 3 to form a pink, water soluble ternary complex which shows maximum absorption at 507 nm with a molar absorptivity of 1.4 x10 L.molcm. The calibration curve is linear in the concentration range 5– 150 μg of bismuth (III) in a final volume of 20ml (i.e. 0.25-7.5 μg ml) with a determination coefficient of (R) (0.9974). The limit of detection (LOD) and the limit of quantification (LOQ) are 0.0671 and 0.2235 μg.mL, respectively. Under optimum conditions, the stoichiometry of the reaction between bismuth (III), alizarin red S and cetylpyridinium chloride is found to be 1:3:6, respectively. The recoveries are obtained in the range of 98.8102.1% and a relative standard deviation (RSD) of ± 0.93 to ±3.07% depending on the concentration level. The proposed method has been applied successfully to the determination of bismuth (III) in various samples such as, natural waters, urine and veterinary preparation.