On-fibre photodegradation studies of polychlorinated biphenyls using SPME–GC–MS–MS: a new approach M. Lores * , M. Llompart, R. Gonz alez-Garc  ıa, C. Gonz alez-Barreiro, R. Cela * Analytical Chemistry Department, University of Santiago de Compostela, Avda. de las Ciencias, E-15706 Santiago de Compostela, Spain Received 13 April 2001; received in revised form 30 November 2001; accepted 4 December 2001 Abstract The known advantages of solid-phase microextraction as a simple, one-step, rapid and solvent free extraction technique are exploited to study the photodegradation kinetics of polychlorinated biphenyls ‘‘on-fibre’’. The obtained results show the possibilities of this new approach not only to monitor the photolysis pathways of such compounds but to determine the photoproducts produced at different irradiation times and/or wavelengths. Photoproducts of PCB decomposition were less chlorinated biphenyls, among them some coplanar congeners have been found, which is im- portant from a toxicological point of view. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Photolysis; Polychlorinated biphenyls; Solid-phase microextraction; GC–MS–MS 1. Introduction Polychlorinated biphenyls (PCBs) are highly toxic ubiquitous contaminants of water, soils and sediments and are quite recalcitrant to biodegradation and direct solar photodegradation. Incineration, unless very care- fully controlled, leads to their partial oxidation to the even more toxic polychlorinated benzofurans and diox- ins, while landfill disposal leads to the pollution of groundwater (Halmann, 1996). The unique thermal and chemical stability that made PCBs industrially useful has also made them a threat to the environment (Hawari et al., 1992). Because all chlorobiphenyls are poorly soluble in water, early work on PCB photochemistry was carried out in alkanes and alcohols, but these solvents, especially the alkanes, are poor mimics of water, the environmental liquid; there- fore, some work in aqueous photochemistry has been done as well (Pagni and Sigman, 1999). The main decomposition mechanism is reductive dechlorination [1–10], and depending on the solvent used, some solvent derivatives can also be found: hy- droxy-derivatives (Crosby and Moilanen, 1973; Pagni and Sigman, 1999), methoxylated products (Ruzo et al., 1974) cyclohexyl-PCBs (L epine et al., 1991, 1992), but no PCB-solvent adducts are found in alkaline 2-propa- nol (Hawari et al., 1992) nor in isooctane (Bunce et al., 1978) neither in hexane (Ruzo et al., 1974; Miao et al., 1999).Mostofthisliteraturearebasictheoreticalstudies of UV-irradiated PCBs decomposition pathways in ho- mogeneous media. The PCBs photochemistry in heterogeneous media hasalsobeeninvestigated,mainlyfortworeasons:(1)to lead to an understanding of the mechanisms by which PCBs adsorbed on soils and other solids photodegrade in the environment, and (2) to develop methods using solid semiconductor photocatalysts such as titanium dioxide to remove PCBs from contaminated matrices (Pagni and Sigman, 1999). The ‘‘on-fibre’’ photodegradation studies of PCBs described in this paper does not belong strictly to ho- mogeneous or heterogeneous photochemistry. On-fibre photochemistry is a new analytical approach that could Chemosphere 47 (2002) 607–615 www.elsevier.com/locate/chemosphere * Corresponding authors. Tel.: +34-981-4563100; fax: +34- 981-547141. E-mail address: qnmlores@usc.es (M. Lores). 0045-6535/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0045-6535(01)00334-4