Dispersive liquid–liquid microextraction for the microvolume spectrophotometric determination of bismuth in pharmaceutical and human serum samples

Abstract

A new dispersive liquid–liquid microextraction (DLLME) method coupled with microvolume UV-vis spectrophotometry was developed for the determination of trace amounts of bismuth. The method is based on the complex formation of Bi(III) with iodide (BiI₄⁻) and extraction into carbon tetrachloride as an ion pair. The extraction is assisted by methyltrioctylammonium chloride, which also acts as a disperser agent. The effect of important parameters, such as the concentration of sulfuric acid and iodide in the sample solution, the amount of methyltrioctylammonium chloride, and the type and volume of extraction solvent were investigated and optimized. The present method is capable of determining bismuth in the concentration range of 5 to 400 ng mL⁻¹ with a limit of detection (LOD) of 1.6 ng mL⁻¹. The relative standard deviation for eight replicate measurements of Bi(III) at concentrations of 200 and 75 ng mL⁻¹ was calculated to be 1.14 and 2.66%, respectively. The developed method was successfully applied to the determination of bismuth in bismuth subcitrate tablets and human serum samples.