The analysis of the majority of the tested active ingredients is mastered by the laboratories. However, there were increased quantification errors for some active ingredients.
The insect repellent icaridin was represented for the first time in this 31st performance assessment, as was the active ingredient clopyralid. The active ingredient azadirachtin had already been tested in an earlier assessment, in which some laboratories had problems with detection. In this respect, an improvement was seen in the current performance assessment: Nevertheless, the active ingredient could still not be correctly quantified eight times (seven of them by recognized laboratories) and was not found five times by laboratories in the recognition process.
One focus of the performance assessments is metabolite analysis. Here, different points are tested. On the one hand, whether the legal residue definition of the sum value was calculated correctly and, on the other hand, whether the laboratories can identify and correctly quantify the individual metabolites of the residue definition. The blueberry sample therefore contained the folpet metabolite phthalimide, the captan metabolite THPI and the growth regulators 1 naphthylacetic acid and 1-naphthylacetamide. These two active ingredients are also covered by a common residue definition. There were considerable deficiencies in the identification and quantification of all the active substances mentioned. In some cases, the substances were not included in the test spectra of the laboratories. This is critical for the monitoring of maximum residue levels, as the legal residue definition for the sum value cannot be fully covered and evaluated. There is a need for improvement here.
Nicotine, a contaminant that is supposed to be screened via the multi-method and requires a single method for accurate quantification in case of a positive result, was not quantified correctly by seven laboratories (five of which were recognized laboratories) and not found by ten laboratories (five of which were recognized laboratories). In some recognized laboratories, nicotine was not included in the spectrum, which means that they did not implement the QS specifications for this active ingredient.
The anomalies found in the test are discussed with the laboratories at the annual meeting of laboratory managers and must be promptly included in future routine tests.
