For the active substances formetanate, pyridalyl and the methiocarb metabolites, more quantification errors were found. In some cases, there were large overestimations, which can be explained by the positive matrix effects present with these substances. In these cases, it becomes clear how important tests such as the QS laboratory performance assessments are. This is the only way laboratories can gain further experience and train their skills.
Laboratories faced similar challenges with the single active ingredient ethephon: here, too, there were almost exclusively over-findings. The measurement accuracy of a single method is normally significantly lower. The test results show that the laboratories concerned need to revalidate this method of determination.
In addition to the analytical question, the current QS laboratory performance assessment focused on the calculation of total active substances. Individual metabolites had to be identified. For some, the application of a factor is necessary to calculate the correct sum residue definition of the active substance. Potential for optimization was also identified here.
