Residue analysis, immunochemical technology

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. 

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. 

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. 

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. 

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. 

How Can We Avoid "Turf Wars" in the Immunoassay Field A major problem that the technology has faced over the last decade has been that there were too few assays. It has been difficult to justify the amount of time needed to learn the technology to analytical laboratories when there are so few applications. We still are in a situation where far too few assays exist. Certainly over the next few years additional groups entering the field will be of great assistance, and we soon will be to the point where enough assays exist for it to be attractive for a residue laboratory to devote a component of its resources to immunochemical analysis. 

---