Ultrasound-assisted dispersive micro-solid phase extraction of Pb(II) in water samples with in situ synthesis of magnetic Fe3O4-PbS nanocomposites followed by electrothermal atomic absorption spectrometry determination

Herein, an ultrasound-assisted dispersive magnetic micro-solid phase extraction (DM-μSPE) approach, along with electrothermal atomic absorption spectrometry (ETAAS) for the determination of lead at trace level in spring, well, river mineral and tap water samples was developed. The extraction step is based on the synthesis of PbS, following the sonochemical decomposition of L-cysteine used as sulphide precursor and its anchoring onto bare magnetite nanoparticles yielding the Fe3O4@PbS nanocomposite. Overall, DM-μSPE with in situ precipitation of PbS and retention onto magnetic sorbent requires a time as short as 6 min. After trapping Pb(II) as PbS, the magnetic nanocomposite was easily separated from the aqueous matrix by applying an external magnetic field and analyzed by ETAAS following slurry sampling. Different parameters involved in both the sorbent preparation/extraction and Pb quantification were optimized. Under optimal conditions, the method showed a detection limit of 0.02 μg L−1 Pb and a quantification limit of 0.07 μg L−1 Pb. The repeatability, expressed as relative standard deviation was 2% (for 0.6 μg L−1; n = 3). An experimental enrichment factor of 79 and an extraction efficiency of 99% were obtained. Finally, the method was applied for the determination of ultratrace levels of Pb(II) in spring, well, river mineral and tap water samples, showing quantitative recoveries in the range of 95–100%.