Linear alkylbenzenes (LABs) are discharged into the environment as sub-products of linear alkylbenzenesulfonate (LAS) detergent. Their association with LAS is attributed to the incomplete sulfonation of the LABs in detergent manufacturing resulting in products having LAB. Recently there has been widespread interest in their use as markers of sewage effluent in the aquatic environment. Although LABs may be potentially useful in assessing the distribution and degradation of domestic wastewater, studies about it are still limited probably due to the analytical difficulties. In this article, a new analytical method for the determination of LABs in detergents using gas chromatography coupled to mass spectrometry (GC-MS) in combination with solid phase microextraction (SPME) is proposed. This alternative sample preparation technology presents several advantages, since it is solvent free, fast, uses the whole sample for analysis, requires only small amounts of sample and the fibers for the extraction procedure are reusable. A factorial experimental design was utilized to obtain the optimum values for the main operational parameters in the analysis of LABs in detergents using direct SPME in the pre-concentration step. (c) 2006 Elsevier B.V. All rights reserved.5622152157