Pesticide residue analysis immunochemical methods

Aston, J.P., D. Britton, M. Wraith, and A. Wright (1992). Immunochemical methods for pesticide residue analysis. In T. Cairns and J. 

The enzyme-linked Immunosorbent assay (ELISA) is a rapid Immunochemical procedure which can be used for trace analysis. We have applied the procedure to paraquat and other compounds difficult to analyze by the more classical methods. The Immunoassay for paraquat shows the practicality of the method for fortified and actual residue samples, and Is being compared with a gas chromatography procedure. Our work with the ELISA Illustrates that the Immunochemical technology can be used to solve problems encountered In pesticide residue analysis. 

Immunochemical methods are rapidly gaining acceptance as analytical techniques for pesticide residue analysis. Unlike most quantitative methods for measuring pesticides, they are simple, rapid, precise, cost effective, and adaptable to laboratory or field situations. The technique centers around the development of an antibody for the pesticide or environmental contaminant of interest. The work hinges on the synthesis of a hapten which contains the functional groups necessary for recognition by the antibody. Once this aspect is complete, immunochemical detection methods may take many forms. The enzyme-linked immunosorbent assay (ELISA) is one form that has been found useful in residue applications. This technique will be illustrated by examples from this laboratory, particularly molinate, a thiocarbamate herbicide used in rice culture. Immunoassay development will be traced from hapten synthesis to validation and field testing of the final assay. 

This table illustrates one of the major impediments to the rapid assimilation of immunochemical technology into pesticide residue analysis labs. Because of the amount and variety of work involved, new method development costs may be high when compared to routine chromatographic methods. However, the low cost per run allows for rapid recovery of the initial investment with sufficiently high sample loads. For example, the cost of reagents and supplies for an ELISA for diflubenzuron was estimated to be 0.20/sample as compared with 4 for HPLC or 11 for GC (35). In addition to the lower reagent and supply costs, the major economic advantage of immunoassay is the dramatic decrease in labor costs. 

M.J. Wraith, D.W. Britton, Immunochemical Methods for Pesticide Residue Analysis , Brighton Crop Protection Conference, British Crop Protection Council, London, 131-137,1988. 

Wraith, M. J. Britton, D. W. Immunochemical methods for pesticide residue analysis. Brighton CropProL Conf.-Pests IMs., (1), 131-7. 1988. 

Several qualitative and quantitative immunochemical methods and their application to the analysis of environmental samples have been described for OP insecticides, a family that includes widely used pesticides such as azinphos-ethyl/methyl, dichlorvos, fenitrothion or fenthion, malathion, mevinphos, and parathion. Mercader and Montoya202 produced monoclonal antibodies against azinphos-methyl and developed an ELISA that was used for the analysis of water samples from different sources, reaching detectability levels near 0.05 pg I. Watanabe et al.203 reported the production of polyclonal antibodies and ELISA procedures to analyze fenitrothion in river, tap, and mineral water (LOD = 0.3 pg L ). Banks et al.204 produced polyclonal antibodies against dichlorvos, an organophosphate insecticide used for stored grain, which also cross-reacts with fenitrothion. Nishi et al.205 reported the first immunoassay for malathion. Residues of this insecticide have... 

Immunochemical methods have also been applied to the detection of bound pesticide residues in soil. These are formed by binding of pesticides to the organic matter of the soil, mainly humic and fulvic acids, and cannot be analyzed using common extraction and assay methods. Hahn et al. used Fab fragments labeled with a fluorescent dye to detect nonextractable residues of atrazine in soil from corn fields. The fluorescence signal obtained was related to the amount of bound atrazine in native soil samples determined by GC after supercritical methanol extraction. A noncompetitive sandwich lA for the analysis of bound residues based on HA-Ab and triazine Ab was developed by Ulrich et HA was extracted from soil, bound to the plates by the HA-Ab and the nonextractable triazine residues were detected by... 

Recent trends in pesticide analysis in food aims for reduced sample pretreatments or simplified methodologies (as QuEChERS approaches), the use of online purification processes, the use of new adsorbents (such as molecular imprinted polymers (MIPs) and nanomaterials) for the extraction and clean-up processes, and focused on the development of large multiresidue methods, most of them based on LC-MS/ MS. In spite of the relevant role of LC-MS/MS, GC-MS-based methods still play an important role in pesticide analysis in food. Despite the development achieved in the immunochemical approaches, the need for multi-residue methods has supported the development and use of instrumental techniques. 

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