Determination of bismuth in pharmaceutical products by resonance light scattering using quaternary ammonium salts as molecular probe

Resonance light scattering (RLS) of bismuth-iodide-quaternary ammonium salts and their analytical application have been studied. Bismuth can react with a large excess of I- to form [BiI4](-) in the presence of Tween-20; [BiI4](-) further reacts with quaternary ammonium salts such as tetramethyl ammonium bromide (TMAB), tetrapropyl ammonium bromide (TPAB) and tetrabutyl ammonium bromide (TBAB) to form an ion-association compound. Moreover, the characteristics of RLS spectra of the complexes, the optimum conditions and the influencing factors have been investigated. The method has been applied to determine Bi(III) in pharmaceutical products with satisfactory results which are in agreement with that of atomic absorbance spectrometry (AAS).