Supramolecular solvent dispersive liquid–liquid microextraction based on solidification of floating drop and graphite furnace atomic absorption spectrometry for the determination of trace lead in food and water samples

Abstract

A novel, sensitive and environmentally friendly supramolecular solvent dispersive liquid–liquid microextraction method based on the solidification of a floating drop was developed for the preconcentration of trace lead (Pb) prior to its determination by graphite furnace atomic absorption spectrometry. In this method, a supramolecular solvent, a coacervate of reverse micelles formed by decanoic acid (DeA) dispersed in tetrahydrofuran (THF)–water mixture, was used to extract the metal chelate produced from the reaction of Pb(II) with diethyldithiocarbamate. After centrifugation, the coacervate phase floated on the surface of the solution, and was then solidified in an ice bath to favor phase separation. Several parameters that affect the extraction efficiency, such as the amount of DeA, the volume of THF, the pH of the sample solution, the concentration of the chelating agent, the extraction time and coexisting ions were systematically investigated. Under the optimized conditions, the linearity of the calibration curve was in the Pb concentration range of 0.1–30 ng mL⁻¹ with a correlation coefficient (R²) of 0.9995. The detection limit of this method for Pb was 27 ng L⁻¹ with an enhancement factor of 52, and the relative standard deviations for 1.0 ng mL⁻¹ and 20 ng mL⁻¹ of Pb were 3.2% and 2.5%, respectively. The method was successfully applied in the determination of trace amounts of Pb in food and water samples.