Biosensors for the Detection of Organophosphorous Pesticides

Organochlorine pesticides were commercially manufactured and used extensively in agriculture worldwide until 1970. The recognition of the health and safety hazards posed by them imposed severe restrictions on their use leading to their discontinuance, and other classes of pesticides such as organophosphates and carbamates were developed. Organophosphorous (OP) pesticides are more water soluble compared with chlorinated pesticides and pose a threat to aquatic life. Toxicity effects of OP pesticides on human beings are well illustrated by Briggs and the Rachael Carson Council. It is essential to monitor the levels of these pesticides, as they cause severe health hazards even at trace levels. Contamination of OP pesticides in food may occur through plants treated with pesticides which are fed to animals during growth and also grains containing pesticide residues that survive through preservation. Contamination of OP pesticides may also occur in water due to pesticide spray in the field that may enter water through leaching. The agricultural chemicals commonly labeled as pesticides are the largest group of poisonous substances being disseminated throughout our environment. The term "pesticide" denotes any agent intended for preventing, destroying, repelling, or mitigating any pest, and this classification may be subdivided into groups such as insecticides, acaricides, nematacides, herbicides, avicides, rodenticides, molluscicides, etc., depending on the species of pest. In the Association of Official Analytical Chemists (AOAC) meeting held in Washington, DC, in 1993 the shortage of new pesticide residue analysis methods for human samples such as blood, urine, and mother's milk was highlighted. It was also emphasized that compared with food, agricultural and environmental samples, development of analytical methodologies for human samples is very much needed for all pesticide classes. During 1993 and 1994 analytical methods were published for 18 pesticides and metabolites in drinking water in the low- to mid-ppb range by the HPLC-UV method and ethyl enethiourea residues in water at 6 to 100 ppm by GC nitrogenphosphorous selective (thermionic) detection method. Some of the newer methods needed for the analysis of pesticide metabolites and bound pesticide residues are listed below.