Determination of Phthalate Esters in Water and Coffee by Solid-Phase Microextraction Using Vinyl Terminated Imidazolium Based Ionic Liquid Grafted on Graphene Oxide Coatings

A series of novel ionic liquids (1-(3-aminopropyl)-3-vinyl imidazolium bromide/tetrafluoroborate) grafted onto graphene oxide- coated stainless-steel wires by a sol-gel technique were fabricated and used as solid-phase microextraction (SPME) fibers for the determination of phthalate esters (PAEs) in water and coffee by a direct immersion-SPME-gas chromatography-mass spectrometry (DI-SPME-GC-MS) method. The effect of pH, stirring rate, ionic strength, extraction temperature and extraction time were examined for each home-made fiber. Under optimized conditions, the proposed method displayed wide linearity (0.01-500 mu g L-1), good repeatability (0.26-13.30%; n=3), and low limit of detections (LODs, 5-30 ng L-1). The home-made fibers had good durability and could be used for more than 120 sorption/desorption cycles. The fiber-to-fiber reproducibility was in the range of 1.53-4.53% for 100 mu g L-1. The method was successfully performed on tap water, seawater and coffee samples with recoveries from 87.6 to 100.7%. The extraction efficiencies of home-made SPME fibers were satisfactorily comparable with those of PA and CAR/PDMS commercial SPME fibers.