▎ 摘　　要

A sensitive and simple method using azo-phenol ligand functionalized magnetic graphene oxide nanosheets, as an adsorbent, has been successfully developed for extraction and preconcentration of trace amounts of cadmium. The prepared nanosheets were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry and transmission electron microscopy, respectively. The main factors affecting the recovery such as the sample pH, adsorbent amount, eluent concentration, time of sonication and coexisting ions have been investigated to optimize the extraction process. The adsorption equilibrium data obeyed the Freundlich model and the kinetic data were well fitted to the pseudo-second-order model. Thermodynamic studies revealed the feasibility and endothermic nature of the system. Under the optimal conditions, the calibration curve was plotted for standard cadmium ion solutions. The testing range was 0.5-12,000 mu gL(-1) and the linear range established between 1 and 10,000 mu gL(-1). Detection limit obtained was 0.4 mu gL(-1). The relative standard deviation was found to be less than 3.32%. The method was further evaluated to analyze different food samples including rice, barley, milk and fish with and without artificially added Cd (adding level: 20-40 mu gL(-1)). The results for analysis of these foods showed that the contamination levels of Cd in rice, barley and fish were 10.17 +/- 0.37, 11.50 +/- 0.35 and 20.00 +/- 1.1 mu gL(-1) respectively, but not found in milk.