Microextraction in packed syringe by using a three-dimensional carbon nanotube/carbon nanofiber–graphene nanostructure coupled to dispersive liquid-liquid microextraction for the determination of phthalate esters in water samples

Abstract

Microextraction in packed syringe (MEPS) was combined with dispersive liquid-liquid microextraction (DLLME) for the extraction of phthalate esters (PEs) from water samples prior to their determination by GC with flame ionization detection. A three-dimensional nanomaterial composed of carbon nanotubes, carbon nanofibers and graphene was prepared by chemical vapor deposition (CVD) and employed as a sorbent for MEPS. The porous structure of the sorbent has been revealed by scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller adsorption. The effects of various experimental variables on the extraction efficiencies of the following PEs were studied: Dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, di-n-butyl phthalate, and di-2-ethylhexyl phthalate. After extraction, the GC assay gives a linear calibration plot that covers the 0.02 to 200 ng mL−1 PE concentration ranges. The method displays detection limits (at an S/N ratio of 3) in the range from 1 to 10 ng mL−1. Relative standard deviations for intra-day and inter-day precision are between 5.7 and 8.9%, and between 7.6 and 10.1%, respectively. The feasibility of the method was demonstrated by extracting and determining PEs in (spiked) real water samples, whereby recoveries in the range of 90.3–98.8% and RSD% lower than 10.3% were attained.