Investigation of the photochemical behaviour of pyrethroids lacking the cyclopropane ring by photo-solid-phase microextraction and gas chromatography/mass spectrometry Maria Fernandez-Alvarez 1 , Maria Llompart 1 , Carmen Garcia-Jares 1 , Thierry Dagnac 2 and Marta Lores 1 * 1 Departamento de Quimica Analitica, Nutricion y Bromatologia, Instituto de Investigacion y Analisis Alimentario, Campus Sur, Universidad de Santiago de Compostela, E-15706 Santiago de Compostela, Spain 2 INGACAL (Galician Institute for Food Quality)-CIAM (Agrarian and Agronomic Research Centre), Laboratory of Food/Feed Safety and Organic Contaminants, Apartado 10, E-15080 A Corun ˜a, Spain Received 5 July 2009; Revised 17 September 2009; Accepted 23 September 2009 The characterization of by-products arising from the UV photodegradation of two insecticide pyrethroids lacking the cyclopropane ring (flucythrinate and fenvalerate) has been investigated by gas chromatography coupled with mass spectrometry (GC/MS). Twenty photoproducts were tentatively identified mainly based on the interpretation of the experimental mass spectra or by using reference mass spectra. Some of these compounds had not previously been detected. Furthermore, the generation of some of the photoproducts might be a matter for concern due to their potential toxicity. The corresponding photodegradation routes, including postulation of the intermediate radicals, have also been proposed. These photodegradation studies were performed by photo-solid-phase micro- extraction (photo-SPME) in which the SPME fibre was exposed to light after extraction of the target analytes from aqueous solutions. The degradation kinetics of the investigated pyrethroids and the photoformation-photodegradation curves of the photoproducts generated in situ were also monitored through the ion chromatograms obtained for different irradiation times and the corresponding mass spectra. Copyright # 2009 John Wiley & Sons, Ltd. The use of synthetic pesticides in agriculture is still the most widespread method for pest control. In order to understand, predict and assess the environmental fate of these com- pounds, it is important to know their distribution and degradation routes in the different compartments. Biode- gradation is often the main route in soil, while abiotic degradation is preeminent in air and water. All abiotic degradation processes, with the exception of hydrolysis and abiotic reduction, are initiated by solar radiation and may be classified, in a broad sense, as photochemical processes. 1 Therefore, the rate of these photolytic transformations and the biological and toxicological impact of the resulting photoproducts are of great importance. Several years ago, photo-solid-phase microextraction (photo-SPME) was proposed as a support for phototrans- formation studies of organic compounds such as musks, 2 polychlorinated biphenyls, 3 and organochlorine 4 and pyre- throid pesticides. 5,6 In photo-SPME, the organic analytes are extracted and then directly photodegraded on the SPME fibre coating, so that the whole system (parent compounds and photoproducts) can be analyzed simultaneously, and this brings many advantages compared with classical photodegradation studies. 7 The pyrethroid insecticides exert excellent control of many different insect species at low cost to the user. In agricultural crops where a broad spectrum of pests can occur, alternative compounds are often more expensive and frequently have to be combined to provide an acceptable spectrum of control. Thus, the benefits of the pyrethroids have led to their extensive and often exclusive use in many of these crops around the world. 8 Fenvalerate [(RS)-a-cyano-3-phenoxy- benzyl-(RS)-2-(4-chlorophenyl)-3-methylbutyrate] and flu- cythrinate [(RS)-a-cyano-3-phenoxybenzyl-(RS)-2-(4-difluo- romethoxyphenyl)-3-methylbutyrate] (Table 1) are pyrethroids used in agriculture on a wide range of crops, including cotton, vines, fruit, olives and cereals, for the control of insect pests belonging to different families such as Lepidoptera, Homoptera and Coleoptera. 9 One of their special features is that both lack the familiar cyclopropane ring functionality associated with other important synthetic pyrethroids such as permethrin and deltamethrin. The degradation of fenvalerate under different types of radiations has been investigated, 10–18 but only a few papers have been published on the photodegradation of flucythri- nate. 19,20 The photodecay of these pyrethroids has been RAPID COMMUNICATIONS IN MASS SPECTROMETRY Rapid Commun. Mass Spectrom. 2009; 23: 3673–3687 Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/rcm.4301 *Correspondence to: M. Lores, Departamento de Quimica Anali- tica, Nutricion y Bromatologia, Instituto de Investigacion y Analisis Alimentario, Campus Sur, Universidad de Santiago de Compostela, E-15706 Santiago de Compostela, Spain. E-mail: marta.lores@usc.es Copyright # 2009 John Wiley & Sons, Ltd.