Mixed hemi-micelle solid-phase extraction based on modified magnetic nanoparticles for extraction of cadmium and lead from food and water samples.

A simple and rapid method for the separation and preconcentration of trace amounts of Cd(ll) and Pb(ll) in milk powder and water samples by magnetic SPE has been developed. The application of silica- coated magnetite nanoparticles (SCMNPs), modified with an anionic surfactant as an effective sorbent material for the microextractioh and determination of trace amounts of Cd(ll)and Pb(ll) from food samples was investigated. The synthesized SCMNPs modified with sodium dodecyl sulfate have the ability to adsolubilize the metal ions after complexation with 1-(2-pyridylazo)-2-naphthol. These magnetic nanoparticles which are carrying the target metals can be easily separated from the aqueous solution by applying an external magnetic field, and the complexed metals can be desorbed using a proper eluent. The effect of pH, concentration of complexing agent, eluent, extraction time, capacity, and desorp tion conditions were investigated. Under the optimized conditions, preconcentration of a 50.0 mL sample solution permitted the LODs of 0.147 and 2.02 μg/L; and the RSDs (n = 7) for 0.05 μg/mL of Cd(ll) and 0.2 μg/mL of Pb(ll) were 2.96 and 1.3%, respectively. The maximum sorption capacity was 8.8 and 9.5 mglg for Cd(ll) and Pb(ll), respectively.