Fig. 5.

Representative MRM chromatograms of SW5 samples, non-spiked and spiked with a mixture of KAR₁ (a) and KAR₂ (b) at two concentrations (0.5 and 1 μmol/l). Reproducibility is shown in triplicates (1st injection blue, second injection red, third injection black). In the boxes, representative calibration curves constructed from five SW matrix-based solutions spiked with a mixture of KAR₁ and KAR₂ at known concentrations (0, 0.25, 0.5, 0.75 and 1.0 μmol/l). The samples were analysed by UHPLC-ESI(+)-MS/MS using the standard addition method