Pesticide Immunoassay

Pesticides are used globally for enhancing crop yields. However, their excessive use/misuse, especially in the developing countries, results in widespread food and environmental contamination. The presence of pesticide residues in food and environment has posed a serious threat to human health and caused a great concern. In order to keep human from being affected, analytical and monitoring system of pesticide residues in food and environment must be developed. Conventional methods employed to detect/analyze the pesticide residue are chromatographic techniques such as gas chromatography (GC), high performance liquid chromatography (HPLC), which are time consuming and require sophisticated equipment only available in well-equipped laboratories. In addition, the conventional methods usually require a lot of complex pre-treatment of samples. Therefore, convenient and rapid pesticide detection system is urgently needed. Immunoassay (IA) technology is such an analysis system with simple, rapid and cost-effective characteristics and widely used in pesticides detection. Thus, the topic of “pesticide immunoassay” will be introduced in this chapter. An "immunoassay" is a quantitative or qualitative method of analysis for a substance which relies on an antibody (Ab), or mixture of antibodies, as the analytical reagent. Antibodies are a class of proteins with the unique ability to bind with high specificity to one or a very limited group of molecules. A molecule that binds to an antibody is called an antigen (Ag). In addition to binding specificity, another important feature of immunoassays is its ability to produce a measurable signal in response to a specific binding. Most immunoassays today depend on the use of an analytical reagent that is associated with a detectable label, such as radioactive elements, enzymes and so on. Immunoassay has a rather long history and has become a widely accepted technique, particularly in the clinical area. Beginning in the middle 1950's, Berson and Yalow were investigating the disease, diabetes. To test the hypothesis that diabetic individuals eliminated insulin too rapidly, they injected radio-labelled insulin into normal and diabetic subjects, and found that the radio-labelled insulin was actually cleared more slowly in diabetics. Then, they begin to experiment with combinations of labelled and unlabeled insulin, and found the phenomenon of competition between labelled and unlabeled insulin. Using the same principles, they described the first radioimmunoassay and this work was considered as the beginning of modern immunoassay (Herzog, 1997). The use of enzymes for labels in immunochemical reactions dates back to the mid-sixties when enzyme-labelled antibodies were applied to the identification and localization of