Last Updated: 19-10-2020 15:50
Within the framework of the HBM4EU project, an interlaboratory comparison was organised for the determination of nine pesticide biomarkers in urine. Included were biomarkers for glyphosate and AMPA (glyphosate and AMPA), chlorpyrifos (TCPy), and pyrethroids (3-PBA, 4-F-3-PBA, cis-DBCA, cis-DCCA, trans-DCCA, and ClF3CA).
The study was performed in January 2020 and was conducted to assess the comparability and reliability of analytical methods across the participating expert laboratories.
The HBM4EU QAU had selected four expert laboratories for pesticide biomarkers in urine. The expert laboratories were from four different countries in Europe. For glyphosate/AMPA, two additional laboratories analysed the samples (lab preparing the control material and an external laboratory).
Each participant received two control materials of human urine to be analysed for glyphosate and AMPA (0.2-2.5 ng/ml), and two other control materials, which both contained the chlorpyrifos biomarker (1-5 ng/ml) and pyrethroid biomarkers (0.1-0.6 ng/ml). The laboratories were requested to perform a single analysis and the submit results to the organiser within 3-4 weeks.
A first assessment of comparability of results was done by calculation of the mean, the RSD, and the relative uncertainty of the mean. Results were compared against the mean through a Z-score when the relative uncertainty of the mean was within 17.5%. In case the relative uncertainty exceeded this value, no objective reliable quantitative comparability assessment could be done.
For glyphosate and AMPA, all six laboratories reported results for glyphosate, and five for AMPA. Results were comparable at the higher level, and for AMPA also at the lower level.
For the chlorpyrifos and pyrethroid biomarkers, all four laboratories reported results for all biomarkers, with one exception (ClF3CA, three labs). In all cases the relative uncertainty of the mean was too high for a quantitative assessment of comparability. This appeared to be caused mainly by results submitted by one laboratory, however, due to the small number of laboratories, it was not possible to classify it as outlier. For information, the results were also assessed after exclusion of the apparent outlier.
Recommendations were made to improve comparability of results in the next round.