Last Updated: 03-04-2020 8:54
Within the framework of the HBM4EU project, an External Quality Assurance Scheme (EQUAS) and an Inter-laboratory Comparison Investigation (ICI) was organized and conducted for the analysis of aromatic amines (AA) in urine.
The study was performed from May 2019 until July 2019. In total, 18 laboratories were invited for this 1st EQUAS/ICI Round, of which nine laboratories from four countries registered. Eight laboratories submitted results yielding in a participation rate of 89 %.
In May 2019, six different test samples of low and high concentration, consisting of 8 mL urine spiked with aromatic amines were sent on dry ice to the participating expert laboratories for single analysis. Candidate laboratories received six samples, three for the low and high concentration levels, respectively, for single analysis. The HBM4EU QAU selected four expert laboratories for analysis of aromatic amines in urine (at least three per parameter).
Assessment of the control material according to Thompson (2006) confirmed the adequate homogeneity for all substances except for 4,4’-methylenebis(2-chloraniline) (MOCA). However, with additional allowance for sampling errors and repeatability, homogeneity for MOCA was sufficient (Fearn and Thompson, 2001). No significant instability was detected for the aromatic amines investigated, except for ortho-toluidine (TOL) in both levels. The decrease in concentration over time was considered when calculating Z-Scores.
The performance of the laboratories was assessed by calculating Z-Scores using the assigned value, mean of expert laboratories (EQUAS) or robust mean of all participants (ICI), and a fixed fit-for-purpose target standard deviation of 25 %. Assigned values and thus Z-scores could be calculated for all aromatic amines except for aniline (AN), since the requirements for evaluating the Z-Scores were not met. For 2,6-TDAHigh and MOCALow, the assigned value was determined using the consensus value of the ICI (SOP HBM4EU-SOP-QA-003).