Abstract: A molecularly imprinted polymer (MIP) base on the surface of graphite oxide (GO) has been developed for the selective recognition of di(2-ethylhexyl)phthalate (DEHP), and applied for the extraction of DEHP in a milk bag sample, with detection by high-performance liquid chromatography. The surface-molecularly imprinted material was prepared by precipitation polymerization in N,N-dimethylformamide (DMF) solvent, using GO as the supporting material, DEHP as the template molecule, and methacrylic acid (MAA) as the functional monomer; the synthesis conditions were also optimized. The obtained GO-MAA-MIP was characterized by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The adsorption properties of the product were evaluated by adsorption experiments, including adsorption isotherms, kinetics, selectivity, saturated adsorption capacity, adsorption equilibrium time, and reusability. Under optimized conditions, DEHP was effectively extracted in the real sample (milk bag) and detected by HPLC. Linearity was obtained with a correlation coefficient (R²) of 0.9979 in a linear range of 0.5-50 mg/L. The limits of detection and quantitation were 0.03 mg/L and 0.1 mg/L, respectively. The average recoveries of the spiked samples at three concentration levels of DEHP ranged from 81.6% to 92.4% with relative standard deviations (RSDs) less than 7%. The results indicated that the proposed GO-MAA-MIP-SPE (solid phase extraction) protocol with HPLC-UV detection could be applied for the selective analysis of DEHP in real samples.

Key words: di(2-ethylhexyl)phthalate (DEHP), graphite oxide (GO), milk plastic bags, solid phase extraction (SPE), surface molecularly imprinted polymer (SMIPs)