Fabrication of magnetic microsphere-confined graphene for the preconcentration of some phthalate esters from environmental water and soybean milk samples followed by their determination by HPLC

In this study, a magnetic microsphere-confined graphene (Fe 3 O 4 @SiO 2 -G) was prepared as a novel adsorbent for the preconcentration of some phthalate esters in environmental water and soybean milk samples prior to high performance liquid chromatography analysis. The properties and morphology of the Fe 3 O 4 @SiO 2 -G were characterized by transmission electron microscopy and X-ray diffraction. This novel graphene-based magnetic nanocomposite showed great adsorptive ability toward the analytes. The method, which takes the advantages of both the high adsorption capacity of G and easy phase separation of the magnetic adsorbent from the sample solution, could avoid the time-consuming experimental procedures related to the traditional solid phase extraction . Various experimental parameters that could affect the extraction efficiencies, such as the amount of Fe 3 O 4 @SiO 2 -G, the extraction time, the pH of sample solution and the desorption conditions, were investigated. Under the optimum conditions, the limits of detection ( S / N =3) of the method for the compounds were between 0.07 and 0.10   ng   mL −1 in water samples, and between 0.15 and 0.30   ng   mL −1 in soybean milk samples. The relative standard deviations (RSDs) varied from 2.7% to 6.1% ( n =5). The recoveries of the method were in the range between 87.2% and 109.0% for environmental water and soybean milk samples. The method is suitable to determine the five phthalate esters (diallyl phthalate, di- n -propyl-phthalate, benzyl butyl phthalate, dicyclohexyl-phthalate and diethyl-hexyl-phthalate) in environmental water and soybean milk samples.