SOLID-PHASE EXTRACTION OF PHTHALATE ESTERS FROM AQUEOUS SAMPLES USING MESOPOROUS SILICA-COATED MULTIWALLED CARBON NANOTUBES AND THEIR DETERMINATION BY HPLC

We report a novel solid-phase extraction adsorbent for the preconcentration of three phthalate esters (PAEs) from aqueous samples. The material was obtained by modifying multiwalled carbon nanotubes (MWCNTs) with mesoporous silica. The structural characterization of the adsorbent was conducted by Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM) and N-2 adsorption-desorption measurement, which confirmed the successful coating of mesoporous silica on MWCNTs and the adsorbent possessing large surface and porous structure. The effects of adsorbent amount, type and volume of eluent and sample pH on extraction efficiency were optimized. Following extraction, the PAEs were quantified by high performance liquid chromatography (HPLC). Under optimal conditions, the recoveries ranged from 89.8% to 96.3%. The calibration plot was linear in the 3-1000 ng.mL(-1) concentration range, with correlation coefficients ranging from 0.9993 to 0.9995. The repeatability of the method, expressed as relative standard deviation (RSD), ranged from 3.8% to 7.7% (for n = 5). Limits of detection (LODs) were between 0.28 ng mL(-1) and 0.53 ng.mL(-1). The relative recoveries (RR) for spiked river water, pond water and tap water samples were in the ranges of 80.9-98.0%, 82.7-96.1% and 88.3-95.5%, respectively. The results showed that the method obviously had a large potential for preconcentration and determination of PAEs in environmental samples.