Surfactant-Assisted Microextraction Method for Spectrophotometric Determination of Bismuth

A liquid-phase microextraction combined with ultraviolet-visible region spectrophotometry was introduced for the preconcentration of Bi(III) in pharmaceutical and sewage wastewater samples. The methodology is based on the chemical interaction of Bi(III) ions with the quaternary ammonium nitrogen-containing reagent, cetyltrimethylammonium bromide (CTAB), in the 1,2-dichloroethane phase as a [( \({\text{BiCl}}_{4}^{ - }\) )(CTA⁺)] complex in hydrochloric acid media. Several analytical parameters that affect the extraction efficiency were studied, including acidity, the amount and volume of reagents, and foreign ions. The molar absorptivity (6.25 × 10⁴ L/(mol cm)), linear range (0.3–5 mg/L with R² = 0.9981), limits of detection (0.02 mg/L), and limits of quantitation (0.08 mg/L) were calculated using the maximum absorbance values at 310 nm for Bi(III). The proposed method was tested on pharmaceutical and wastewater samples, and the results showed recoveries ranging from 93 to 107%.