Quantification of PCBs in Environmental Samples: Comparison of Results Obtained with Different Analytical Instruments (GC—ECD, GC—MS) and Standards

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Abstract
Polychlorinated biphenyls have been determined in sediments, macroalgae, mussels and worms sampled in the lagoon of Venice, Italy. Sample preparation included hexane extraction, clean-up with sulphuric acid, Florisil and copper and separation from pesticides by column chromatography with silica gel. Analyses were performed using methylsilicone and phenyl-methylsilicone capillary columns. A GC—ECD and a computer-assisted GC—MS performing selected ion monitoring (SIM) were employed. Quantification was based on standards prepared by combining Aroclor formulations and on mixtures prepared with selected biphenyls of different degree of chlorination (7 PCB mix). Recovery tests conducted with an internal standard added to the samples before extraction yielded values between 79 and 102%. The precisions obtained on quadruplicate samples by using the combination HRGC—LRMS with Aroclor standards and with the 7 PCB mix were 18% and 15%, respectively. Imprecision was mainly due to uncertainties in measuring areas of low-intensity SIM peaks. With HRGC—ECD precisions were better than 7%. A systematic overestimation was observed with HRGC—ECD, probably due to inclusion of interfering compounds.