A simple, sensitive, and accurate method for the determination of methyl tert-butyl ether (MTBE) in water samples has been developed based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-flame ionization detection (GC-FID). A sol–gel based coating fiber using poly(ethylene glycol) (PEG) grafted onto multi-walled carbon nanotubes (PEG-g-MWCNTs) as the extraction phase was prepared and used for the extraction of MTBE. The relative standard deviations (RSDs) for one fiber (repeatability) (n ¼ 6) and between fibers or batch to batch (reproducibility) (n ¼ 3) were obtained. The repeatability was assessed at low (0.1 ng mL 1) and high (100 ng mL 1) concentrations and the RSDs obtained were 5.3 and 4.1%, respectively. The reproducibility obtained for a concentration of 0.1 ng mL 1 was 6.5%. The calibration curve of MTBE was linear in the range from 0.07 to 500 ng mL 1. The limits of detection (S/N ¼ 3) of 0.01 ng mL 1 and the limits of quantification (S/N ¼ 10) of 0.07 ng mL 1 were obtained. The developed method was applied successfully to determine trace level of MTBE in real water samples. The relative recoveries for the spiked samples with 5 ng mL 1 of MTBE were ranged from 91 to 112% and the relative standard deviations were less than 7.8%. Introduction

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