Optimization of ultrasound-assisted magnetic retrieval-linked ionic liquid dispersive liquid–liquid microextraction for the determination of cadmium and lead in water samples by graphite furnace atomic absorption spectrometry

A simple and efficient method for the determination of Cd and Pb in water samples was developed by ultrasound-assisted magnetic retrieval-linked ionic liquid dispersive liquid–liquid microextraction (UA-MR-IL-DLLME) preconcentration and graphite furnace atomic absorption spectrometry (GFAAS) detection. Ionic liquid (IL) [Hmim] [PF 6 ] was used as the extractant, ammonium pyrrolidine dithiocarbamate (APDC) as the complexing agent and Fe 3 O 4 nanoparticles as the sorbent, while ultrasound was applied to assist the dispersion of the extractant and accelerate the mass transfer process. The effect of different factors on the extraction efficiency including pH, IL volume, APDC amount, ultrasound extraction time, ultrasound desorption time and Fe 3 O 4 amount was studied by a fractional factorial design to screen for the most important factors. Then a central composite design was used to optimize the significant factors. Under the optimal conditions, the method has linear calibration curves over the range of 0.3–20   ng/mL for Cd and 0.5–40   ng/mL for Pb, with correlation coefficients (R) of 0.9990 and 0.9986 for Cd and Pb, respectively. The limits of detection were 0.1   ng/mL and 0.15   ng/mL with relative standard deviations of 3.4% and 2.8% for Cd and Pb, respectively. Finally, the method was successfully applied for the determination of Cd and Pb in the real water samples and satisfactory recoveries were achieved.