Pre-concentration and determination of cadmium and lead ions in real water, soil and food samples using a simple and sensitive green solvent-based ultrasonic assisted dispersive liquid-liquid microextraction and graphite furnace atomic absorption spectrometry

A novel green solvent-based ultrasonic assisted dispersive liquid-liquid microextraction (GS-UADLLME) method was developed for the preconcentration of cadmium and lead ions in various real samples prior to determination by graphite furnace atomic absorption spectrometry (GFAAS). In order to extract trace amounts of cadmium and lead ions, 2-amino-3-sulfhydrylpropanoic acid (l-cysteine) (as a green ligand), tetrafluoroborate ion (BF4-) (as an ion pair agent) and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] (as acceptor phase) were used. Different effective factors in the microextraction procedure such as pH of the sample solution, sample solution volume, acceptor phase volume, l-cysteine and tetrafluoroborate concentrations, centrifugation conditions and salting addition were thoroughly optimized. Under the optimum conditions, the calibration graphs were linear in the range of 0.8-180 and 2.5-190 ng L-1 with a correlation coefficient (r(2)) higher than 0.9967 for the measurement of cadmium and lead ions, respectively. The limits of detection for the determination of Cd(ii) and Pb(ii) for the proposed method were 0.2 and 0.7 ng L-1, respectively. The relative standard deviations (n = 5) for the analyte determination were lower than 3.4%. In order to investigate the method's accuracy, cadmium and lead contents of a certified reference material, SRM 1643e (NIST), were determined and the results from the proposed method were in very good agreement with the certified values. The suggested method was successfully applied to the determination of cadmium and lead ions in real samples such as real water, soil, rice and tea samples.