An Interlaboratory Comparative Study on the Quantitative Determination of Glyphosate at Low Levels in Wheat Flour

In recent years, the use of glyphosate has dramatically increased worldwide, and there is growing concern about contamination of organic products caused by its heavy use on neighboring fields. Glyphosate is found as a residue not only in soil, plants, and groundwater but also in humans and animals. Considering the controversy on glyphosate maximum residue level in foodstuff and the difficulties in its analytical determination, the main purpose of the present paper was to investigate the competence and accuracy of 13 accredited European laboratories in determining glyphosate in wheat flour at a level close to their reporting limit of 10 μg/kg. According to the results of this performance assessment, the laboratories were not able to quantify glyphosate at trace levels. Therefore, their specified reporting limits of 10 μg/kg were not supported by their results, and a reporting limit of around 50 μg/kg of glyphosate in flour seems to be more appropriate to guarantee reliable and robust results. The widespread use of glyphosate and its harmfulness to humans make its detection at trace levels a primary goal for analytical laboratories. This is achievable through the improvement of QA and/or the optimization of the method of analysis used for glyphosate detection.