Voltammetric Analysis of Pesticides

Pollution due to pesticides is a daily and growing problem, closely related to the intensification of agricultural activities devoted to the satisfaction of human needs in terms of food. In fact, throughout the world, pesticides are intensively used as defoliants or against weed and pests in a large variety of crops (Castanho et al., 2003; De Souza & Machado, 2005a). Also known as persistent organic pollutants due to their low solubility and degradation in the environment, pesticides are thus inherently toxic since their accumulation in living organisms can induce serious diseases. Several analytical techniques have been used for the analysis of pesticides, which include fluorimetry (Anson & Wade, 1976; Eremin et al., 1996; Coly & Aaron, 1998a,b), capillary electrophoresis (Tomita et al., 1992; Pico et al., 2003), spectrophotometry (Shivhare & Gupta, 1991; Jain et al., 1993), mass spectroscopy (Moyano & Galceran, 1996; Leandro et al., 2006) and mainly gas or liquid chromatography (McGarvey, 1993; Castro et al., 2000; Fillion et al., 2000; Corasaniti & Nistico, 1993). These techniques operate quite well but they present a certain number of disadvantages: they are limited to laboratories, time consuming, expensive, and have to be performed by highly trained technicians (Mulchandani, 2001). During the past decade, scientific works devoted to the implementation of electrochemical devices suitable for the sensing of pesticides have gained growing interest. The main proposal of these studies is the development of convenient, sensitive, selective and low cost tools that could be exploited for a rapid monitoring of pesticides (Tapsoba et al. 2009; Tcheumi et al., 2010). In fact, when pesticides are applied, only a small fraction actually reaches target organisms formed by crop pests and vectors of diseases. Consequently, traces amounts of these chemicals can be detected in surrounding and ground water, in the soil and in the air. Scheme 1 summarizes the most common pathways involved in the dissemination of pesticides in the environment. In another hand, the determination of pesticides and their residues or metabolites in either water or soil solutions is a critical problem for several reasons: (i) the number of chemicals involved is too large, (ii) each of these chemicals displays a specificity in term of reactivity, and (iii) several active ingredients of pesticides are often present in the same matrix. Therefore, the need to design convenient tools for the electroanalysis of pesticides in environmental matrices and in food remains a permanent and challenging question. Following these lines, there is an interest to properly adapt electrochemical methods to build sensors, due to some of their advantageous characteristics such as simple operations, short analysis times, accuracy and high sensitivity (Parham & Rahbar, 2010; Tcheumi et al., 2010).