Mesoporous Silica-coated Magnetic Nanoparticles for Mixed Hemimicelles Solid-phase Extraction of Phthalate Esters in Environmental Water Samples with Liquid Chromatographic Analysis

To extract, preconcentrate and determine the trace level of environmental contaminants, a novel mixed hemimicelles solid-phase extraction (MHSPE) method based on mesoporous silica-coated magnetic nanoparticles (Fe3O4/meso-SiO2 NPs) as adsorbent was developed for extraction of phthalate esters from water samples. The Fe3O4/meso-SiO2 NPs were synthesized by using a combination of hydrothermal method and sol-gel method. The obtained Fe3O4/meso-SiO2 NPs possessed a large surface area (570 m(2)/g), superparamagnetism, and uniform mesopores (2.8 nm). MHSPE parameters, such as the amount of surfactant, pH of sample, shaking and separation time, eluent and breakthrough volume that may influence the extraction of analytes greatly, were further investigated. Under the optimized conditions, the extraction was completed in 20 min and a concentration factor of 500 was achieved by extracting 250 mL water sample. Detection limits obtained of butyl-benzyl phthalate (BBP), di-n-butyl phthalate (DnBP), di-(2-ethylhexyl) phthalate (DEHP) and di-n-cotyl phthalate (DnOP) were 12, 21, 12, and 32 ng/L, respectively. The proposed method exhibited high extraction efficiency and relatively short time for extracting the target compounds.