Confirmatory method definition

To demonstrate the validity of an analytical method, data regarding working range/ calibration, recovery, repeatability, specificity and LOQ have to be provided for each relevant sample matrix. Most often these data have to be collected from several studies, e.g., from several validation reports of the developer of the method, the independent laboratory validation or the confirmatory method trials. If the intended use of a pesticide is not restricted to one matrix type and if residues are transferred via feedstuffs to animals and finally to foodstuffs of animal origin, up to 30 sets of the quality parameters described above are necessary for each analyte of the residue definition. Table 2 can be used as a checklist to monitor the completeness of required data. 

After due consideration of the control experiments carried out in the studies on collagen and gelatin and of the fact that no 3-aspartyl linkages have been reported, it seems unlikely that any a —> 7 conversion has occurred. In the case of other proteins it also seems unlikely but, in view of the fairly low values obtained and the small but significant value given by poly-a-glutamic acid by the method of Haurowitz et al. (1957), confirmatory experiments using methods similar to those of Franzblau (1962) and Franzblau et al. (1963) are necessary before any definite conclusions can be drawn. 

Confirm with several alternate tests. All test results should be consistent with each other and with the proposed method results. Where a definitive confirmation is not available or feasible, other methods can be used. In this case, more than one confirmatory test may be required to provide the certainty of identification. The confirmatory tests selected should be based on different principles from the pri-... 

LC-MS methods have proved very satisfactory as alternatives to the LC-FL method for precise analysis ofYTXs. There are advantages in the simple sample preparation and wider range of analogues detected. However, the greater instrument costs can only be justified if LC-MS is used for quantitative multitoxin analysis where definitive results are obtained for YTXs and a range of other toxin classes in a single run without the need for further confirmatory analyses. Several such methods have been developed and validated. " ... 

Comparative serology a relative standard of comparison. It may be impractical, technically difficult, or impossible to obtain definitive proof of infection via culture or isolation techniques. In the absence of such a gold standard, less exacting methods must serve as the standard of comparison with the new assay. If the other tests have already established assay performance characteristics (e.g., the Rose Bengal screening test followed by the complement fixation confirmatory test for detection of antibody to Brucella bovis), their results taken together provide a useful composite-based standard by which the new assay may be compared. 

TLC with visualization using a modified Griess reagent. The ability of this method to provide a definitive identification has been questioned because of the false positives that may be observed from totally unrelated compounds. When TLC is employed for the examination of explosives residues it is therefore recommended that further confirmatory analyses should be carried out before the presence of explosives is reported. 

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