Headspace solid-phase microextraction for the determination of polychlorinated biphenyls in soils and sediments

A headspace solid-phase microextraction (HSSPME) method has been developed for the quantification of polychlorinated biphenyls (PCBs) in soils and sed iments. In this study polydimethylsiloxane fibers with a 100 mu m thickness were used. Parameters affecting the extension of the adsorption process we re studied (sampling time, sample size, volume of water and acetone added t o the sample, volume of headspace, and extraction temperature). Because the time for reaching equilibrium between phases takes several hours, it was n ecessary to work in nonequilibrium conditions to keep the sample analysis t o a reasonable time. Soil and sediment samples were weighed in a glass vial and, after the addition of 1 mt of water and a stirring magnetic bar, the vial was closed and heated to 100 degrees C. The sample was stirred and the SPME fiber was exposed to the headspace over the soil-water slurry for 30 min. Finally, the fiber was inserted in the gas chromatograph (GC) injector port and GC-mass selective detector analysis was carried out. The proposed HSSPME method exhibits excellent linearity, sensitivity, and precision. Th e detection limit was in the subnanogram per gram level, and repeatability tests showed a relative standard deviation below 10%. This method has been applied to two real contaminated sediments. In these real samples, standard addition calibrations were done and the concentrations of PCBs found with the proposed method were in good agreement with the certified PCB values. ( C) 1999 John Wiley & Sons, Inc.