The Potential of Flow-Based Optosensing Devices for Pesticide Assessment

Abstract

The rise of intensive agriculture in the last decades has originated the massive use of pesticides (herbicides, fungicides or insecticides), which has become a serious environmental problem and a potential risk for human health. Pesticides residues can be often found in soils, natural waters, atmosphere and agricultural products and cause adverse effects on humans, plants, animals and ecosystems, even at low concentration levels. In order to guarantee consumer safety and regulate international trade, Maximum Residue Limits (MRLs) for pesticides in foodstuffs have been established by several Government agencies and European Union Commission (European Union, 2005). Therefore, nowadays the development of new analytical methodologies capable of determining trace levels of pesticides in the environment is one of the most important tasks in analytical science. The determination of pesticide residues in food matrices is a formidable challenge mainly because of the small quantities of analytes and large amounts of interfering substances which can be co-extracted with them and, in most cases, adversely affect the results of an analysis (Wilkowska & Biziuk, 2011). Pesticide analysis in food samples has been usually carried out by means of multi-residue methods that use gas chromatography (GC) as the preferred technique because many of these compounds are low polar, volatile and thermally stable (Guan et al., 2010; Hunter et al., 2010). Nevertheless, new pesticides, which show a more specific mode of action and have a higher polarity and lower persistence than old ones, have been developed in the last years. Most of these novel compounds can be conveniently separated by high-performance liquid chromatography (HPLC) (Fu et al., 2009; Soler et al., 2008; Wu et al., 2002). Currently, pesticides comprise more than 1200 active ingredients, which are formulated in thousand of different commercial products (Ahmed, 2001). Since they present very different physic-chemical characteristics and large differences in volatility, polarity and persistence, both GC and HPLC coupled to mass spectrometry detection (GC-MS, HPLC-MS) are used as complementary techniques in pesticide analysis (Garrido et al., 2005; Pang et al., 2006). Nevertheless, although pesticide residue analysis methodologies in different matrices by GC and/or HPLC are well established, there is still a need for sensitive, faster, easy-to-use and cost effective procedures as real and practical alternatives to the robust and efficient chromatographic methods. These procedures would allow the rapid detection of pesticides, being used for a preliminary screening in laboratories where a large number of samples have to be processed in a short time. In response to this need, several spectroscopic