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 alizarine 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 a maximum absorption at 507 nm with a molar absorptivity of 1.4 x104 L.mol-1cm-1. The calibration curve is linear in the concentration range 5 150 g of bismuth (III) in a final volume of 20mL (i.e. 0.25-7.5 g mL-1) with a determination coefficient of (R2) (0.9974). The limit of detection (LOD) and the limit of quantification (LOQ) are 0.0671 and 0.2235 g.mL-1, respectively. Under optimum conditions, the stoichiometry of the reaction between bismuth (III), alizarine red S and cetylpyridinium chloride is found to be 1:3:6, respectively. The recoveries are obtained in the range of 98.8- 102.1% 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