Preparation of an L-Cysteine Functionalized Magnetic Nanosorbent for the Sensitive Quantification of Heavy Metal Ions in Food by Graphite Furnace Atomic Absorption Spectrometry

A typical l-cysteine functionalized magnetic mesoporous nanosorbent (Cys-Si-MNPs) was successfully synthesized and characterized by transmission electron microscopy, the nitrogen adsorption-desorption isotherm and X-ray photoelectron spectroscopy. The results showed that Fe3O4 magnetic core was shelled by mesoporous silica, and the capacity of thiol group with strong affinity to various heavy metal ions was as high as 238 mg g(-1). Using the obtained l-cysteine functionalized magnetic nanoparticles as the adsorbent, a graphite furnace atomic absorption spectrometry (GFAAS) method was developed for the determination of Pb2+, Cd2+, Cu2+, Cr3+, and V5+ in food. The experimental parameters affecting the separation performance including the pH of the sample solution, adsorbent mass, contact time, and co-existing ions were investigated systematically. Using the optimized conditions, the detection limits were as low as from 0.006 to 0.36 mu g L-1. The precision of the method was evaluated by the relative standard deviation (n = 11) at limit of quantification (LOQ) of each target ion and was less than 6.0%. The proposed method was further successfully applied for the determination of the target ions in certified reference materials including GBW10043 rice, GBW 10023 laver, and GBW 10050 shrimp. The obtained recoveries were in the range from 89% to 102% with relative standard deviations (n = 3) lower than 8%.