Magnetic molecularly imprinted polymer nanoparticles-based solid-phase extraction coupled with gas chromatography-mass spectrometry for selective determination of trace di-(2-ethylhexyl) phthalate in water samples

Novel magnetic molecularly imprinted polymer nanoparticles (MMIPs) were synthesized by surface imprinting technology with a sol-gel process, using di(2-ethylhexyl)phthalate (DEHP) as the template. The MMIPs were characterized using Fourier transform-infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The MMIPs displayed good adsorption selectivity for DEHP, with selectivity coefficients of 5.2 and 4.8 with respect to di-n-octyl phthalate and dibutyl phthalate, respectively. The reusability of MMIPs was demonstrated for at least eight repeated cycles without significant loss in adsorption capacity. A novel method for selective preconcentration and determination of trace DEHP in aqueous solutions was developed by using the magnetic DEHP-imprinted nanoparticles as adsorbent for solid-phase extraction (SPE) coupled with gas chromatography-mass spectrometry (GC-MS). The optimum SPE conditions were as follows: adsorbent amount, 50 mg; sample volume, 100 mL; adsorption time, 20 min; eluent, chloroform; and desorption time, 5 min. Results showed that the limit of detection (LOD) and limit of quantification (LOQ) for DEHP were 0.02 and 0.075 μg L^-1, respectively. The proposed method was applied to the determination of DEHP in different real water samples, with spiked recovery of 93.3-103.2 % and RSD of 1.2-3.2 %. Therefore, the developed analytical method is rapid, sensitive, and accurate, which provides a new option for the detection of trace DEHP in aqueous samples.