Analytica Chimica Acta 569 (2006) 103–112 A fast extraction technique for extracting polycyclic aromatic hydrocarbons (PAHs) from lichens samples used as biomonitors of air pollution: Dynamic sonication versus other methods C. Dome ˜ no, M. Blasco, C. S´ anchez, C. Ner´ ın ∗ Grupo GUIA-Instituto de Investigaci´ on de Ingenier´ ıa en Arag´ on (I3A), Department Qu´ ımica Anal´ ıtica, Centro Superior de Ingenieros (CPS), Mar´ ıa de Luna 3, 50018 Zaragoza, Spain Received 22 November 2005; received in revised form 13 March 2006; accepted 15 March 2006 Available online 22 March 2006 Abstract A fast method for the extraction of polycyclic aromatic hydrocarbons, PAHs, in lichens used as biomonitors of air pollution is optimized and further applied to real lichen samples. The method consists of using the dynamic sonication-assisted solvent extraction. The lichen sample is introduced in a cell through which the extracting solvent pass at 0.2 mL/min. Sixteen PAHs were extracted from 0.2 g of dried lichens, Xanthoria parietina, in 10 min with a total extraction volume of 2 mL of hexane. The extracted fraction, previously concentrated to 500 L, was analyzed by GC–MS without any clean-up step following extraction. Both spiked and non-spiked native samples were used for the evaluation. The procedure compared with the static ultrasonic and Soxhlet extraction, showed high efficiency with respect to both recoveries, time and solvent consumption and for all the 16 PAHs recoveries higher than 70% were obtained. The limit of detection of the investigated PAHs was in the range of 0.021–0.032 g/g. The linear range of the entire method was 0.115–1.805 g/g. for all the investigated PAHs. An application of the method was demonstrated with the extraction of lichens samples collected from an urban area. Twelve out of 16 investigated PAHs were found. © 2006 Elsevier B.V. All rights reserved. Keywords: Extraction; Dynamic sonication extraction; Analysis; PAHs; GC–MS; Lichens 1. Introduction The process of environmental air analysis is a difficult task in the step of sample handling and monitoring, because of expen- sive air sampling and analyzing equipments are needed [1–6]. An advantageous technique is the use of pollution bioindicators and/or bioaccumulators which permit an easier sampling and facilitate the sample treatment and analysis steps in laboratory [7–10]. Bioindicators are organisms that respond to certain level of pollution by a change in their life cycle or accumulation of the particular pollutant. For air pollution assessment, pine needles [12], marine algae [13], lichens and mosses [11,12], may be con- sidered as the most commonly applied bioindicator organisms. Lichens as bioindicators and/or bioaccumulators of air pol- lution were used before in several studies, during the last 30 ∗ Corresponding author. Tel.: +34 976 761873; fax: +34 976 762388. E-mail address: cnerin@unizar.es (C. Ner´ ın). years, since Hawksworth & Rose in 1970 related SO 2 concen- tration with the presence/absence of lichens in an area [14]. More recently lichens were used to biomonitor trace element contam- ination in Pisa Province (Tuscany, Italy) [15] and in Veneto (NE Italy) [16], to determine depositions of heavy metals in the Shet- land Islands (Antarctica) [17] and Zinc concentrations in western Ireland [13] and in Finland [18]. Other examples of lichens used as bioindicators and/or bioaccumulators were to identify PAHs, phenols and trace metals in the Holy Cross Mountains (South- Central Poland) [19] and to biomonitor 210 Po and 210 Pb around a coal-fired power plant in western Turkey [20]. Lichens are defined as a symbiotic association between a fun- gus and an alga. They do not have roots, leafs or flowers so they take water and nutrients directly from the atmosphere but also other substances from air, like atmospheric pollutants. These ones are not well-spent and are accumulated in their tissues [7]. For this reason lichens have bioaccumulator capacity and high sensitivity towards specific pollutants. Pollution effects in lichens are shown in the decrease of sorts of lichens number due 0003-2670/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2006.03.053