Ultrasonic-enhanced preconcentration of trace Pb(II) using hydrophobic, lighter-than-water ionic liquid microextraction combined with solidification of the aqueous solution prior to detection by graphite furnace atomic absorption spectrometry in human fluids

摘要

Herein, we adopted a hydrophobic, lighter-than-water phosphonium-based ionic liquid (LTWP-IL) for preconcentration of trace Pb(II)-dithizone complexes prior to detection by graphite furnace atomic absorption spectrometry (GFAAS) in human fluids. Because the solvent injected into GFAAS contained LTWP-IL phase, the routine pyrolysis temperature such as 300-400 degrees C was not appropriate for LTWP-IL, and the optimized pyrolysis and atomization temperatures of Pb(II) were 800 degrees C and 1800 degrees C, respectively. The hydrophobic LTWP-IL floats on the surface of the aqueous phase after centrifugation, which allows for convenient and complete collection after solidification of the aqueous phase (HLILM-SAP), and thus overcomes the prominent disadvantage of conventional heavier-than-water ionic liquids-based microextraction. Ultrasound was used to disperse hydrophobic LTWP-IL in the absence of a dispersive solvent. Several operational parameters were optimized using a one-factor at a fime approach: LTWP-IL extractant, 30 mu L; chelating agent, 0.3% dithizone; ultrasonic time, 5 min; solution pH = 6.0; solidification at - 20 degrees C, 60 min and back extractant, 200 mu L of 0.5 mol L-1 HNO3. Under optimized conditions, limits of detection were as low as 0.014-0.018 mu g L-1 and enrichment factors reached > 43-fold in urine and blood samples. Inter- and intra-day precisions had relative standard deviations of 3.77-6.79%. Trueness was evaluated by determining four certified reference materials of Pb(II) resulting in recovery values of 95-103%. Overall, the HLILM-SAP-GFAAS method is convenient, efficient and robust, making it suitable for rapid and accurate analysis of trace Pb(II) in complex biological fluids.