Cloud Point Extraction of Pesticide Residues

Pesticides including organochlorine pesticides (OCPs), organophosphorus pesticides (OPPs), and nitrogen-containing herbicides are types of well-known environmental contaminants. Pesticides are generally categorized based upon their persistence in the environment. Organochlorine pesticides are considered persistent pesticides. These pesticides have long environmental half-lives and tend to bioaccumulate in humans and other animals. The contemporary pesticides include organophosphates, carbamates, triazines, chloroacetanilides, synthetic pyrethroids, and others and are considered nonpersistent. These pesticides have much shorter environmental half-lives and tend not to bioaccumulate (Barr & Needham, 2002). Table 1 provides a very abbreviated synopsis of major families, or chemical classes, of pesticides grouped by their uses. Among the pesticides, organophosphate and carbamate compounds are the most widely used due to their high insecticidal activity and relatively low persistence (Dyson et al., 2002). These pesticides are toxic because they act as inhibitors of acetylcholinesterase, an enzyme that catalysis in a very efficient way the hydrolysis of the neurotransmitter acetylcholine. This enzyme is present in vertebrates and insects and its inhibition can disrupt the transmission of nerve impulses (Hassal, 1983; Simonian et al., 1997). The increasing production and application of pesticides for agricultural and non-agricultural purposes has caused the pollution of air, soil, ground, and surface water which involves a serious risk to the environment and as well as human health due to either direct exposure or through residues in food and drinking water. In the world, alarming levels of pesticides have been reported in air, water, soil, as well as in foods and biological materials (Pico ́et al., 2003; Lambropoulou & Albanis, 2007; Guzzella et al., 2006; Konstantinou et al., 2006; Núñez et al., 2005; Harner et al., 2006; Chang & Dong, 2006; Barr & Needham, 2002). Nowadays, approximately 300000 tonnes of pesticides per year are used for agricultural production in Europe and their residues can be found in soil, water, foods, etc. For environmental and drinking waters, the maximum admissible concentration of a single compound established by the European Union (EU) is 0.1, and 0.5 μg L−1 is the maximum allowed for the total concentration of all pesticides (http://ec.europa.eu/environment/water). The WHO threshold values for concentrations of pesticides in drinking water, based on toxicological considerations, are less strict than the maximum concentrations allowed by EU (Hamilton et al., 2003). Pesticide residues are highly mobile in soil and can leach into ground-water, so may be a potential health hazard.