Accurate and reliable determination of cadmium (Cd) in vegetables is often difficult due to low concentrations and matrix effects. Magnetic solid-phase extraction (MSPE) was developed for preconcentration and determination of trace amounts of Cd in vegetables and water samples prior to flame atomic absorption spectrometry (FAAS) analysis. Cobalt magnetic nanoparticles were synthesized and modified by sodium dodecyl sulfate (SDS) and 2-(5-bromo-2- pyridylazo)-5-diethyl aminophenol ligand (5-Br-PADAP) through a chemical precipitation method so that the nanoparticles (NPs) could be used as a new sorbent. The NPs bearing the Cd ions were easily separated from the aqueous solution by applying an external magnetic field and the complexed metals were desorbed using dilute HNO3. Extraction conditions including pH, amount of sorbent, contact time, desorption solvent, breakthrough volume, and sorption capacity were optimized. Under optimal conditions, the calibration curve was linear from 1.0–500 ng·mL−1 of Cd, R2 = 0.997. The detection limit was 0.6 ng·mL−1 in the original solution (3 Sb·m−1) and the relative standard deviation for eight replicates determination of 0.1 μg·mL−1 Cd was ±2.2%. Cadmium is easily aggregated in edible parts of leafy vegetables. Heavy metals analysis of vegetables is essential for protection of humanhealth and to comply with regulatory controls.
