Journal of Hazardous Materials B136 (2006) 714–720 Analysis of n-alkanes in water samples by means of headspace solvent microextraction and gas chromatography Mohammadreza Khalili Zanjani, Yadollah Yamini ∗ , Shahab Shariati Department of Chemistry, School of Sciences, Tarbiat Modarres University, P.O. Box 14115-175, Tehran, Iran Received 26 August 2005; received in revised form 25 November 2005; accepted 3 January 2006 Available online 15 February 2006 Abstract A simple and efficient headspace solvent microextraction (HSME) was developed for the simultaneous determination of the trace concentrations of some n-alkanes in water samples. Therefore, a microdrop of an organic solvent was extruded from the needle tip of a gas chromatographic syringe to the headspace above the surface of the solution in a sealed vial. Then the volatile organic compounds are extracted and concentrated in the microdrop. Next, the microdrop was retracted into the microsyringe and injected directly into the gas chromatograph. Experimental parameters which control the performance of HSME such as the type of microextraction solvent, organic drop and sample volume, sample stirring rate, sample solution and microsyringe needle temperatures, salt addition and exposure time profiles were investigated and optimized. Finally, the enrichment factor, dynamic linear range (DLR), limit of detection (LOD) and precision of the method were evaluated. Using optimum extraction conditions, good linearity with correlation coefficients in the range of 0.995 < r 2 < 0.999, suitable precision (%2.3 < R.S.D. < %7.2) and low detection limits (0.1–4.0 g/l) were achieved. The HSME was performed for determination of n-alkanes in different types of natural water samples and acceptable recoveries were obtained. The results demonstrated that HSME is a rapid, accurate and effective sample preparation method and could be successfully applied for the determination of n-alkanes in water samples. © 2006 Elsevier B.V. All rights reserved. Keywords: Headspace solvent microextraction; n-Alkanes; Gas chromatography 1. Introduction Environmental contamination by petroleum hydrocarbons is the most common site contamination issue encountered by environmental professionals [1]. In recent years, environmen- tal pollution by petroleum-type materials has increased with the growth of industries and increased demand for energy [2]. The nature of petroleum hydrocarbon contamination is highly vari- able. Petroleum hydrocarbons themselves are diverse mixtures of chemical components. The more common functional cate- gories of compounds found in petroleum products are n-alkanes, branched alkanes, cycloalkanes and aromatic compounds [1]. Organic contamination results from the uncontrolled releases from manufacturing and refining installations, spillage during transportation, underground storage tanks, above ground storage tanks, pumps or dispensers, fuel lines between the tanks and ∗ Corresponding author. Fax: +98 21 88006544. E-mail address: yyamini@modares.ac.ir (Y. Yamini). pumps, fill points and lines (normally remote from the tanks), air vent pipelines, waste oil tanks, drum storage and filling areas and storm water interceptors [3,4]. It has been estimated that around 20 × 10 6 t of petroleum hydrocarbons (mainly n-alkanes) impact marine waters and estuaries annually [5]. Therefore, analysis of environmental samples polluted by crude oil or petroleum products is important [3]. In order to determine trace level of these pollutants, an extrac- tion and preconcentration step is necessary. The most difficult and time-consuming step in the determination of organic pol- lutants in environmental samples is extraction of the analytes from the matrix [6]. Trace enrichment can be performed by conventional techniques such as liquid–liquid extraction (LLE), purge and trap (P&T), solid-phase extraction (SPE) or solid- phase microextraction (SPME) and liquid phase microextraction (LPME) methods [7]. In view of the analysis of volatile organic compounds in water, conventional LLE often needs large amounts of toxic solvents and time-consuming procedures [8]. P&T method, also known as the dynamic headspace method, removes volatile com- 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2006.01.004