The whole chromatographic windows were divided into three time segments: Segment I is set to waste; Segment II and III are set to source.
Data were collected under positive ionization mode with multiple reactions monitoring (MRM).
2.6. Quantification
The relative quantification method used in this work was established as follows.
Two aliquots of BAs were derivatized by d3-MASC (heavy form) and d0-MASC (light form), respectively.
To construct the calibration curves, d0-MASC and d3-MASC derivatives of standards were mixed in ratios of 1:10–10:1 for all BAs, and analyzed by HPLC–MS/MS.
The linear regression equations were obtained by plotting the experimental peak area ratios of d0-MASC/d3-MASC derivatives (y) against nominal concentration ratios (x).
Slopes of regression equation of calibration curves for the seven derivatives approximated to 1.0, the correlation coefficient values (R2) of above 0.99 were obtained for all the analytes, indicating good correlation of the experimental data with the theoretical ratios (See Supplementary Material Fig. S3).
For real