Trace Determination of Petroleum Pollutants in Water Samples by Dispersive Liquid-Liquid Microextraction Method

Since there is not any report about simultaneous microextraction of 42 petroleum pollutants (n-alkanes and polycyclic aromatic hydrocarbons) in water, in the present study dispersive liquid-liquid microextraction (DLLME) using organic solvents lighter than water was applied for simultaneous determination of these compounds in water samples by GC-flame ionization detection (GC-FID). In order to achieve the best extraction efficiency, optimization of variables affecting DLLME method was carried out. In this method, an appropriate mixture of extraction and disperser solvents is injected into an aqueous sample, which led to formation of a cloudy solution. The analytes become enriched in the extraction solvent, which is dispersed throughout the bulk aqueous sample. After centrifugation, quantification of the analytes in the organic phase can be performed by GC-FID. The main advantage of this technique is its quite large surface area between the fine droplets of the extraction solvent and water sample, and the accordingly fast extraction kinetics that results in the rapid achieving of a state of equilibrium and the high enrichment factors (EFs). Under the optimum conditions, EFs in the range of 280-446 were obtained. The proposed method provided low limits of detection (0.1-0.98mg L-1) and acceptable extraction repeatabilities. It was linear over two orders of magnitude. Finally, petroleum pollutants have been determined in different type of water samples by this method.