74 laboratories from 20 countries took part in the current laboratory performance assessment for residue monitoring. The task was to examine light-colored table grapes for selected active substances, identify them and quantify them correctly. A total of 47 QS-recognized laboratories took part in the test. 44 of them completed the test successfully. This means that the latest laboratory performance assessment for the objective evaluation of laboratories' analytical competence turned out well for the laboratories recognized in the QS scheme. However, the test design was also challenging for them, as evidenced by the number of quantification errors for certain active substances.
The test design light-colored table grapes
The matrix to be examined in this performance assessment were light-colored table grapes, which are classified as easy to moderately difficult. The focus of the test design was on analytics. 13 different active substances, including three active substances flupyradifuron, fluxapyroxad and monocrotophos, which had not previously been tested in any QS assessments. The first two substances are approved in Germany. The fungicide monocrotophos is used worldwide but is already banned in Germany due to its high toxicity (ARfD 0.002 mg/kg/KG bw). Analytically, the active ingredient is challenging, as it is an alkali-labile substance that is already unstable in solution. In addition, the active substance cyantraniliprole had to be detected. It had led to problems with correct analysis in a previous test and is currently the focus of official monitoring programs.
The results
94% of the participating recognized laboratories passed the test, 2/3 of them without any errors. The situation is different for laboratories that are currently undergoing the recognition procedure for the QS scheme. Here, only 58% were able to complete the test successfully, 20% without errors. Two of the three laboratories whose participation in the test was voluntary also passed the test. For the laboratories in the recognition procedure, a successful test result is one part of the recognition process that must be fulfilled. Another part is a document check. Only when both parts have been satisfactorily fulfilled can QS recognition be granted.
The results will be discussed in detail with the participants at the next laboratory managers' meeting in February 2024.
