Abstract: Magnetic graphene oxide (Fe3O4/GO) was successfully prepared from graphite powder and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy (RS). Fe3O4/GO was used as a new purifying agent to improve the traditional method of quick, easy, cheap, effective, rugged, and safe (QuEChERS) for the pretreatment of dairy samples because of its strong adsorption capacity and magnetism. Using the improved pretreatment procedure combined with gas chromatography-mass spectrometry (GC-MS), 16 phthalate esters (PAEs) were analyzed. The optimum pretreatment conditions were determined by optimizing the type of extraction agent and the amount of purifying agent. The results showed that the calibration curves for all PAEs had a good linearity in the concentration range of 20–1 000 μg/L with correlation coefficients (R) ≥ 0.998 4. The lowest limits of detection were between 0.5 and 2.5 μg/kg. The average recoveries ranged from 85.7% to 117.7% at spiked concentration levels of 50, 100 and 200 μg/kg, with relative standard deviation (RSD) not exceeding 7.6%. Two milliliters of organic solvent and 155 mg of adsorbent were required for treatment of 1 g sample, which took about 8 min. The method only needs simple pretreatment and has good impurity removal effects and is suitable for the analysis of PAEs in dairy products.

Key words: magnetic graphene oxide, improved QuEChERS, gas chromatography-mass spectrometry, phthalate esters