Limit of Detection (LOD) and Limit of Quantitation (LOQ)

The calibration solution was diluted 2-fold in turn and analyzed via UHPLC-MRM-MS/MS. The lower limits of detection (LLOD) and quantitation (LLOQ) were determined using the S/N. The LLOD was defined as the compound concentration at which the S/N was 3, and the LLOQ was defined as the compound concentration at which the S/N was 10 (US FDA guideline for bioanalytical method validation). The method’s precision was evaluated by the relative standard deviation (RSD) of repeated injections of QC samples (Table S4) and accuracy was assessed by the recovery rate of QC samples. The spiked recovery rate is the percentage difference between the mean measured concentration and spiked concentration.