Rapid screening of polychlorinated biphenyls in sediments using non-equilibrium solid-phase microextraction and fast gas chromatography with electron-capture detection.
A rapid method for the screening of polychlorinated biphenyls (PCBs) in sediment samples is described. Analytes are concentrated on a poly(dimethylsiloxane) (PDMS) solid-phase microextraction (SPME) fibre, separated using a narrow-bore gas chromatography column (10 m x 0.1mm I.D.) and determined with a micro-electron-capture detector (micro-ECD). The narrow-bore column showed a similar separation efficiency to a conventional capillary one (30 m x 0.32 mm I.D.) and allowed a 3 times reduction in the analysis time. Moreover, thermal desorption of SPME fibres in the narrow-bore column did not produce any degradation in the quality of separations when compared to the split injection mode. The use of an oxidative sample treatment was mandatory to remove sulphur interferences in the chromatograms and increase the yield of PCBs during SPME for short sampling times. Under optimised conditions, a fraction of sediment (0.1-0.5 g) was mixed with 5 ml of a 0.2M potassium permanganate solution and 0.5 ml of sulphuric acid 6M in a 22 ml closed vessel. Sample treatment and headspace SPME of PCBs were performed simultaneously for 10 min at 100 degrees C. Globally, the whole analytical procedure takes about 20 min and presents quantification limits between 0.5 and 1.3 ng/g. Accuracy was evaluated by analysing a reference sediment sample with certified concentrations of several PCBs.