Spring onions a hard nut for labs to crack

Foreign labs are catching up in the latest QS laboratory performance assessment

In autumn 2011, 77 laboratories from twelve countries took part in the laboratory performance assessment for residue monitoring in fruit, vegetables and potatoes. In particular the 28 laboratories undergoing the recognition procedure found themselves faced with a real challenge in the form of the test matrix for spring onions. Only 15 of the 28 labs passed the autumn test. Of the 49 laboratories already recognized on the other hand, none is to lose its recognition.

An interesting aspect of the test results is the development of the international laboratories: while nine foreign labs lost their recognition only a year ago, the recognized foreign laboratories have even done slightly better overall than the recognized German labs in the last two performance assessments. The high standard would appear to be asserting itself internationally too.

Wilfried Kamphausen, QS expert for fruit, vegetables and potatoes, sees a very important function in the frequency of the laboratory performance assessment in particular: Only through the fine-mesh examination of a laboratory’s performance capability have we been able to create a situation in the market in which there is a real demand for competence. The way things stand today, the laboratory performance assessment offers traders an important orientation aid in choosing a competent laboratory. We want to continue to guarantee this high standard of lab work, especially through the performance assessment for QS recognition.

Jens Schäfer, laboratory expert at QS, explains: The complexity of the spring onion matrix with the sulphur compounds and chlorophyll it contains would appear to have made the identification and quantification of the active substances more difficult, even though we deliberately selected conventional pesticides in realistic concentrations. As in the spring tests, the active substance fluazifop-p caused the biggest problems once again. Six laboratories could not identify the active substance at all this time and 22 quantified it wrongly, so there is clear potential for improvement here. The active substance carbendazim from the benzimidazoles group also proved difficult, with quantification posing the greatest challenge for the labs. The active substance p,p-DDE was contained in the test material this time as typical residual waste, but it was in the main fairly easy for the labs to analyze it.

Of the 60 laboratories currently recognized in the QS scheme, 49 participated in the test and 45 passed. The remaining four keep their recognition for the time being, but must take the test again this coming spring because, depending on results, the laboratories are obliged to undergo testing twice a year.