Pre-concentration procedure using dispersive liquid–liquid microextraction for the determination of bismuth by flame atomic absorption spectrometry

Abstract

In this work, an ion-pair dispersive liquid–liquid microextraction (IP-DLLME) procedure for the preconcentration of Bi³⁺ is introduced. In this procedure, 2-(5-bromo-2-pyridylazo)-5-(diethyl amino) phenol reagent as complexing agent and 700 μL of acetone (dispersing solvent) containing 75 μL of dichlorobenzene (extracting solvent) are directly injected into 10 mL of aqueous solution containing Bi³⁺ ions. A cloudy mixture is formed and the Bi³⁺ ions are extracted in fine droplets of the extracting solvent. After extraction, phase separation is performed by rapid centrifugation, and Bi³⁺ is determined in the enriched phase by flame atomic absorption spectrometry (FAAS). Several variable factors that influence the extraction and complex formation such as pH, concentration of 2-(5-bromo-2-pyridylazo)-5-(diethyl amino) phenol, centrifugation time, type and volume of the extracting and dispersing solvent, are optimized. Under the optimized conditions, the detection limit obtained is 3.0 ng mL⁻¹ (3σb) and the relative standard deviation is ±1.5% (C = 0.4 μg mL⁻¹, n = 7). The calibration curve is linear in the range of 30–1700 ng mL⁻¹ of Bi³⁺ and the enrichment factor equals 28.6. The proposed method was successfully applied to the extraction and determination of Bi³⁺ in real and spiked samples.