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

In this work, an ion-pair dispersive liquid-liquid microextraction (IP-DLLME) procedure for the preconcentration of Bi(3+) is introduced. In this procedure, 2-(5-bromo-2-pyridylazo)-5-(diethyl amino) phenol reagent as complexing agent and 700 mu L of acetone (dispersing solvent) containing 75 mu L of dichlorobenzene (extracting solvent) are directly injected into 10 mL of aqueous solution containing Bi(3+) ions. A cloudy mixture is formed and the Bi(3+) 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) (3 sigma b) and the relative standard deviation is +/- 1.5% (C = 0.4 mu g mL(-1), n = 7). The calibration curve is linear in the range of 30-1700 ng mL(-1) of Bi(3+) and the enrichment factor equals 28.6. The proposed method was successfully applied to the extraction and determination of Bi(3+) in real and spiked samples.