Requirements for validating a residue method

To understand how immunoassay-based analytical methods can be constructed to comply with tolerance enforcement requirements, a brief examination of those requirements is in order. This discussion is not intended to be comprehensive but to highlight aspects of special significance to immunoassay method development. The reader is urged to consult the literature for further details. 

A brief summary of EPA method requirements for tolerance enforcement methods is given in Table 1. Taken in total, these requirements ensure that the means to conduct the method are available to laboratories and that experimental evidence to establish method performance, on a substrate-by-substrate basis, is generated prior to analysis of samples and as part of each analytical set. Thus, an analyst who must generate data to support method performance in his or her hands can obtain whatever is required to reproduce the method. 

These requirements have special implications with regard to immunoassay methods. Eirst, the lack of commercial availability of reagents precludes preparing antibody-coated tubes or plates on-site, which may require knowledge of special skills. Commercial availability also ensures the analyst access to a reproducibly manufactured product. Therefore, the method must be based on an immunoassay that is a commercial product. Method developers may choose to introduce an in-house assay to the marketplace by partnering with a manufacturer, although this approach is costly and time-consuming. 

3 Method must not be subject to substrate-related interferences (not require the use of blank 

5 Control and recovery data for all substrates (blank substrate and blank substrate-fortified 

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