HBM4EU ICI report UV-filters in urine round 2

Within the framework of the HBM4EU project, an interlaboratory comparison was organized and conducted for the analysis of benzophenones (BP) in urine. Benzophenones correspond to 4 biomarkers: 2,4-Dihydroxybenzophenone (BP1), 2,2’,4,4’-Tetrahydroxybenzophenone (BP2), 2-Hydroxy-4-methoxybenzophenone (BP3), 5-Chloro-2-hydroxybenzophenone (BP7). However, the problems caused by COVID-19 and technical problems in one of the participating expert laboratories (UEL1) resulted in the reduction of the tested parameters to BP1 and BP3 from this 2nd round on. The study was performed from February to June 2020 due to the impact of COVID-19. The HBM4EU QAU had selected three expert laboratories for benzophenones in urine. All expert laboratories were from different countries in Europe. The participation in this interlaboratory comparison for benzophenones in urine was mandatory for these laboratories. During this 2nd round, one expert laboratory (UEL2) withdrew its participation in the interlaboratory comparisons for BP in urine due to the impact of COVID-19. Two different test samples consisting of 5 mL urine mixed from burdened native material to obtain two different concentrations (BPR2A, BPR2B) were prepared and sent to the participating expert laboratories for single analysis. Homogeneity and stability assessment of the control materials confirmed that the materials were adequately homogeneous. Due to the reduced number of participating expert laboratories, only two results were submitted for each level of each parameter. These two results were considered comparable if the difference to the mean was ≤35% and no Z-scores were calculated. The results of the two participating expert laboratories (UEL1 and UEL5) showed a difference from the mean of 4.6% (BP1R2A), 3.8% (BP1R2B), 8.4% (BP3R2A) and 4.0% (BP3R2B) and were thus in a good comparable range. The final evaluation of the comparability of the respective expert laboratories can, however, only take place upon completion of all interlaboratory comparison rounds.