Residue analysis, immunochemical

The use of immunoassays for the determination of pesticides and veterinary medicines in food animals has increased since the early 1990s. The advantages of simple analysis, quick results, and high throughput make immunoassays a powerful technique for problematic matrices commonly encountered in animal agriculture. Careful development and validation are required to obtain accurate results, however. This review has demonstrated that most immunochemical techniques have been designed for use with milk samples, but a number of applications have also been developed for liver and muscle samples. The development of immunoassay techniques for residue analysis in eggs has clearly not been pursued to the extent of other edible tissues. 

When a more specific detection system is used instead, a rigorous sample cleanup may not be necessary. This is actually the case with most of the microbiological and immunochemical detection systems applied in residue analysis. Owing to the selectivity and sensitivity of their detection principle, homogenization with an aqueous buffer is often tire only treatment required prior to analysis. Moreover, these detection systems are usually independent of the sample size as, in many cases, a single drop of milk or tissue fluid is sufficient to carry out a successful analysis. 

Problems may also arise with respect to specificity when ELISAs are applied for trace residue analysis, because any compound whose molecule is in part identical with or closely similar to the antigenic determinant of the analyte can compete for antibody-binding sites. Therefore, immunochemical methods are valuable for screening and testing purposes but cannot be considered as definitive from a regulatory perspective. For legal enforcement use, these methods should be used as part of an analytical system that consists of additional methods capable of definitively identifying the compounds of interest. 

Immunochemical methods provide a powerful tool in the field of drug residue analysis. The exquisite specificity that can be obtained with immunochemical reagents provides new analytical opportunities that were previously not possible with classic analytical methods and can greatly reduce the amount of sample cleanup required prior to analysis. 

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

In this chapter the potential of several immunochemical techniques for residue analysis will be explored. Sufficient background methodology will be presented to allow the reader to evaluate the advantages and disadvantages of immunochemical techniques and their potential application to residue problems. 

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. 

Triazines such as atrazine, propazine or simazine, are widely used herbicides. Currently, the determination of atrazine in water and soil samples is mainly done by GLC (1,2) or HPLC (3-5). However, these procedures require cumbersome cleanup steps which could be avoided by using immunoassays as an alternative approach to residue analysis. Such immunochemical determination based on competitive binding of herbicides or pesticides to an antibody (6,7), has been described recently for s-... 

Bruce Hammock developed the section on new immunochemical techniques. These chapters describe investigation of disease resistance in plants neuronal development in insect embryos pesticide residue analysis for plant diagnostics and quarantine and the development of a biosensor for applying monoclonal antibodies and microelectronics for environmental analysis. 

In 1980 an article appeared on the Potential of Immunochemical Technology for Pesticide Residue Analysis (2). As evidenced by the articles in this section, that potential is beginning to be realized. However, of greater importance, we can envision far more applications in the future. 

The manuscript by Harrison et. al. provides some examples of immunochemical applications to classical residue analysis. It summarizes some of the advantages and limitations of the technology as it applies to the field and provides an outline for development of the technology in house. 

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. 

Since the use of immunochemical technology for pesticide residue analysis was first reviewed by Ercegovich in 1971 (9) several helpful reviews of this application have been published (11,14,23,33). Despite the potential demonstrated during this period, few researchers and regulators apply immunochemical technology to their own problems in pesticide residue analysis. 

While the use of immunoassay for residue analysis should continue to expand, it is not the answer to all problems in environmental analysis. Immunochemical technology should serve best as a complement to existing methods rather than a replacement for them. It is especially important to recognize the potential of immunoassay for impact in environmental screening through the developments which will be discussed later in this chapter. It is in this area that we expect immunochemical technology to make its greatest contribution to environmental analysis. 

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. 

As an analytical approach to residue analysis, immunoassay methods are not well characterized, and no validation protocols have been established. The Association of Official Analytical Chemists, whose primary purpose is validation of analytical methods, established a Task Force on Test Kits and Proprietary Methods (2), which has addressed some of the issues relating to immunoassay methods. The International Union of Pure and Applied Chemistry s Commission on Food Chemistry has established a Working Group on Immunochemical Methods, whose first project is to develop draft guidelines on criteria for evaluation, validation, and quality control for r o-immunoassay methods (10). Similar guidelines for EIAs will also be developed. These documents will assist in development and standardization of requirements for precision for both between-laboratories and within-laboratory andyses, accuracy, and ruggedness, and— for qualitative methods— false positive and false negative rates. 

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

N. Haagsma and C. van der Water, Immunochemical methods in the analysis of veterinary drug residues, in Analysis of Antibiotic Drug Residues in Food Products of Animal Origin, ed. V. K. Agarwal, Plenum Press, New York, pp. 81-97 (1992). 

Biosensors may provide the basis for in-field analyses and real-time process analysis. However, biosensors are generally limited to the determination of a limited range of analytes in defined matrices. Enzyme-based biosensors, principally acetylcholinesterase (AChE) inhibition, have been successfully used in environmental analysis for residues of dichlorvos and paraoxon, " carbaryl " and carbofuran. " Immunochemically based biosensors may be the basis for the determination of pesticide residues in liquid samples, principally water and environmental samples, but also fruit juices. The sensors can be linked to transducers, for example based on a piezo-... 

---