Up to now the analysis of aqueous samples by ion mobility spectrometry is a challenge due to the lack of suitable sample introduction systems. But just the introduction of asymmetric field strengths leading to a higher selectivity and sensitivity, this technique is of growing interest for on-site analysis of contaminated water. In this work, first results for the preparation of a portable GC-DMS system are presented. A differential mobility spectrometer (DMS) with a 63 Ni ionization source has been used as a detector for the gaschromatographic separation of benzene, toluene, ethylbenzene m-, o-, and p-xylene (BTEX) in water. Separation from the matrix and pre-concentration of the analytes was achieved by solid-phase microextraction (SPME). The influence of the different chromatographic parameters, extraction conditions and differential mobility spectrometry settings on the sensitivity and signal shape were investigated. Results of the optimization of the analytical method as well as analytical validation parameters such as method detection limit, limit of quantification and the repeatability are discussed. Additionally, the applicability of the method was demonstrated by the analysis of a real surface water sample.