Samenvatting

It can be concluded that the HBM4EU serum sample preparation method is suitable for Effect-Directed Analysis. The method allows a recovery of all bioactive compounds of interest from serum in the EDA products, with little loss of compounds: bioassay spectra and chromatograms. Nevertheless, the HBM4EU sample preparation method is suitable to the extent of using low serum concentrations, especially when quantification is part of the chemical analysis. Thus, to avoid ion suppression and a high limit of detection (LOD), which are unfavourable. In parallel, the VU sample preparation method also requires low serum concentrations to avoid a matrix effect.
In comparison to an existing sample preparation method of the Vrije Universiteit Amsterdam, it can be concluded that the HBM4EU method has an overall higher efficacy. The HBM4EU method is two times more effective than the VU method with regard to THDC recoveries in the whole extracts, in terms of T4-equivalence. In this study, the average T4-equivalence using the new sample preparation method was calculated to be of 19.72g/g. In contrast, the average T4-equivalence obtained from the VU sample preparation method was 9.08g/g. The ratio of the recovered THDCs is 2:1 between the methods (HBM4EU:VU). Concerning peak height in chemical analysis, the efficacy of the HBM4EU method could also be qualitatively determined superior than the VU method, with a difference factor of 10. After applying the HBM4EU method, peak heights in the chromatograms vary between values of approximately 2×104 and 3×105.
The chromatograms from the chemical analysis after performing the VU sample preparation method gave peak heights in the range of approximately 3×103 to 5×104. Furthermore, the HBM4EU method is more effective than the VU method with regard to the compound-loss. The VU sample preparation is more vulnerable to loss of compounds, since the method involves more steps. This susceptibility was observed in this study. The HBM4EU sample preparation method recovered all THDCs in the chemical analysis. In other words, all compounds were identified in the chromatograms. Contrary to the HBM4EU sample preparation
method, 2,4,6-TBP was lost in the VU sample preparation, as it was not identified in the chromatograms. Finally, this study provides an indication on the suitability and efficacy of the newly sample preparation method developed by the European HBM4EU initiative for Effect-directed Analysis. Therefore, the method should be further tested for statistical reliability and reproducibility, in order to ascertain its efficacy with regard to other sample preparation methods. Consequently, EDA studies could be performed applying the HBM4EU sample preparation method for human biomonitoring purposes.