Among the active substances that had never been tested before, two active substances were again identified that are analytically challenging for laboratories. Quantification errors occurred more frequently with the active substance mepronil.
Furathiocarb, a metabolite from the residue definition of carbofuran, was not included in the spectrum of multi-method active substances in some laboratories. If furathiocarb is found to be positive, a hydrolysis step is required for the collection of the residue definition. Correct quantification also caused problems for some laboratories. In addition, there were shortcomings in the reporting. Not all laboratories reported the carbofuran sum
specified by the complex residue definition.
The growth regulator 1-naphthylacetamide, which was included for the second time, also caused problems with correct quantification. The synthetic auxin acts as a growth regulator similar to the natural auxin indole-3-acetic acid.
The active substance glyphosate, which was to be analysed using a single method, was included for the second time. This problematic and difficult-to-quantify herbicide caused major problems. It was quantified incorrectly by almost a quarter of the participants, with the majority quantifying it too high. This clearly shows that the proficiency test fulfills its task of identifying problematic active substances. Glyphosate, which tends to cause matrix effects, requires a great deal of analytical experience and expertise.
