Multivariate optimization of a solid phase microextraction-headspace procedure for the determination of benzene, toluene, ethylbenzene and xylenes in effluent samples from a waste treatment plant

A method based on solid-phase microextraction (SPME) and gas chromatography with flame ionization detection (GC-FID) has been optimized for the determination of benzene, toluene, ethylbenzene and xylenes (BTEX) in water released from a waste treatment plant. The extraction step was optimized using fractional factorial and central composite designs including the following experimental factors: saline concentration; extraction time; desorption time; agitation velocity; headspace volume. A multiple function was used to describe the experimental conditions for simultaneous extraction of the compounds. The procedure, based on direct SPME at 50 °C, using a polydimethylsiloxane fiber, showed good linearity (r > 0.997 over a concentration range 2–200 μg L−1) and repeatability (relative standard deviation (RSD) < 4.23%) for all compounds, with limits of detection ranging from 0.05 to 0.28 μg L−1, and limits of quantification ranging from 0.14 to 0.84 μg L−1. Concentrations of the target compounds in these samples were between 145.8 and 1891 μg L−1.