Evaluation of clean-up methods for the determination of chlorinated aromatic hydrocarbons in fly-ash by capillary gas chromatography and mass selective detection

This study describes an evaluation of different clean-up methods for the determination of polychlorinated dibenzo-p-dioxins and-dibenzofurans (PCDD/F extracts of fly-ash. The PCDD/F fractions obtained were additionally investigated for the presence or absence of polychlorinated benzenes (PCBz), polychlorinated biphenyls (PCB) and polychlorinated phenols (PCP) to detect any interference, and to test for determinability in the same fractions. Three different methods were compared, viz. solid phase extraction (SPE) using disposable benzenesulphonic acid and silicagel cartridges, multilayer silicagel plus alumina column chromatography (MLA); and an active carbon method plus multilayer silicagel plus alumina column chromatographic (ACM) method. The fractions obtained were analyzed by capillary gas chromatography and mass selective detection using the isotope dilution method. Both the variances and the levels of PCDD/F showed good agreement between the different clean-up methods investigated. The SPE-method, being fast and simple, should be preferred for the determination of PCDD/F in fly-ash; it also allows the determination of PCBz and PCB in the fractions. The presence of PCBz and PCB in the clean-up fractions does not interfere with the determination of PCDD/F provided that the mass spectra of PCDD/F are checked for [M-COCI] fragments.