Flow-injection analysis spectrophotometric determination of bismuth in environmental and pharmaceutical samples

A new, simple, rapid, selective, and sensitive flow-injection analysis (FIA) method for the spectrophotometric determination of Bi is described. It is based on reaction of Bi (III) with I- ions in the presence of cationic surfactants (CS), i.e., cetylpyridinium chloride, cetyltrimethylammonium bromide, tetradecyltrimethylarnmonium bromide, dodecyltrimethylarnmonium bromide in sulfuric media to give a violet-colored complex. The apparent value of molar absorpitivity of the complex in the terms of Bi with four CSs lie in the range of (1.00-1.20) x 10(4) Lmol(-1)cm(-1) at lambda(max) 490 nm. Among them, the most sensitive CSs, i.e., cetylpyridinium chloride (CPC) has been selected for the detailed studies. The detection limit (causing absorbance > 3 sec) of the method is 65 mug L-1 Bi. The sample throughput of the method is > 120 samples hr(-1). The effect of diverse ions and surfactants in the FIA determination of Bi is examined. The composition of the complex is discussed. The analytical and FIA variables in the determination of Bi are optimized. The method has been applied for analysis of Bi in the environmental and pharmaceutical materials.