Solid phase microextraction for trace analysis of urinary benzene in environmental monitoring
Due to increasing concern about toxic substances such as benzene and its analogs in the environment and workplaces, it is becoming more important to monitor such chemicals in order to evaluate risk hazards and potential problems caused by exposure to toxic compounds (Barcelo et al., 1991; Keymeulen et al., 2001; Sperlingova et al., 2003). Benzene is an important industrial compound because of its widespread usage, occurrence in mineral oil, and also in many combustion processes that cause environmental and industrial pollution (Keymeulen et al., 2001; Shahtaheri et al., 2005). Environmental and Occupational exposure to benzene occurs mainly via inhalation. Relatively high exposure takes place in manual application techniques such as production, distribution, and handling of gasoline. The predominant sources are emissions from vehicles, petrochemical industries, and chemical reactions of organic materials. The classification of benzene as a human carcinogen by the International Agency for Research on Cancer (IARC) has resulted in a reduction in occupational exposure levels and, as a consequence, has led to the need for improved biomonitoring techniques (IARC, 1982). Sample pretreatment for the isolation and environment of organic compounds from aqueous solution is the most challenging and timeconsuming steps in an analytical procedure Mohammadi et al., 2006). Traditionally, liquid- liquid extraction (LLE) (Keith, 1996), solid phase extraction (SPE) (Thurman et al., 1998), has been commonly used for the extraction of compounds from aqueous matrices. For benzene, urinary muconic acid or/and s-phenylmercapturic acid are examined. However, some compound such as ascorbic acid which added to food as a preservative has also a same metabolite (muconic acid) in urine even in the general population.