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. 2022 Feb 10;12(2):167. doi: 10.3390/metabo12020167

Figure 4.

Figure 4

Reproducibility of the matrix QC spiked with MEHP, MEHHP and MEOHP and measured by UHPLC/QTOF over three years, i.e., from 2015 to 2018 (N = 100). The average values ± standard deviation (ng/mL) measured for quality control (QC) samples of standard metabolites were: MEHP: 15.96 ± 1.04; MEHHP: 15.73 ± 1.31; MEOHP: 12.34 ± 0.45, respectively. For BPA we assessed stability and reproducibility in n = 50 QC together with DEHP metabolites in LC/MS analysis and average value was 22.30 ± 1.17 ng/mL and RSD = 5.25%. The low variation of QC samples, prepared at the beginning of the study and stored at −20 °C, showed that DEHP metabolites and BPA are stable also if stored at −20 °C.