A simple and sensitive method for the determination of methyl tert-butyl ether (MTBE) in water using headspace-solid-phase microextraction (HS-SPME) at sub-ng mL(-1) concentrations is described. The analysis was carried out using a cooled SPME fiber coated with a film of dodecylsulfate-doped polypyrrole coupled to ion mobility spectrometry equipped with corona discharge ionization. The headspace-solid-phase microextraction experimental procedures to extract MTBE in water samples were optimized with a dodecylsulfate-doped polypyrrole coated fiber at a 30 min extraction time, extraction temperature of 40 degrees C, sodium chloride concentration of 2.5 mol L-1 and desorption temperature of 140 degrees C. Two linear calibration curves respectively in the ranges of 2-17 ng mL(-1) and 10-70 ng mL(-1) with detection limits of 0.7 ng mL(-1) and 4.9 ng mL(-1) were obtained. Relative standard deviations for three replicates in water samples were <10%. The capability of dodecylsulfate-doped polypyrrole to extract MTBE has been compared with the results obtained based on the literature data for commercial fiber. The results shows that dodecylsulfate-doped polypyrrole, as a solid-phase microextraction fiber coating, is suitable for successful extraction of MTBE having detection limits comparable to what obtained with commercial fibers. Finally, the proposed method was applied to the analysis of MTBE in three ground water samples and regular unleaded gasoline from petrol station in Tehran central district, Iran. (C) 2009 Elsevier B.V. All rights reserved.