Single-residue methods enforcement

On the other hand, single-residue methods developed by the applicants give basic information about appropriate cleanup steps and specific determination procedures. In addition, not many laboratories other than those from the applicants are able to test the real solvent extraction efficiency. The reason is that extraction studies need radio-labeled incurred residues instead of fortified samples. Hence enforcement methods provided by the manufacturers accelerate the development of methods which meet the needs of (official) food control laboratories. 

The extent of validation of confirmatory techniques is currently under consideration. Qne approach is that the extent of validation may be smaller than for the enforcement method. In principle, validation in triplicate at the relevant concentration level (LOQ or MRL) is sufficient. In the case where an MRL is set for multiple crops, a single validation in all representative crop groups is sufficient. A confirmatory method for residues in air is not required if a corresponding method was submitted for the other sample matrices. This approach is realized in Germany. ... 

However, there is no general requirement that enforcement methods need to monitor all metabolites of an active ingredient. The primary purpose of enforcement methods is to detect violations of good agricultural practice. For this purpose, residue levels found in samples from the market (so-called Market Basket Surveys) have to be compared with MRLs, which are derived from residue concentrations found in supervised trials. It is not necessary for this comparison to be based on the total pesticide residue. Most often the choice of a single compound (e.g., parent or primary metabolite) as a marker of the total pesticide residue is more feasible. Method development and the later method application are much easier in that case. Only for intake calculation purposes, e.g., when the daily intake of pesticide residues (calculated from the results... 

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