For quantification of the acids derivatives the most characteris-tic ions with the highest signal were selected as quantitation ions(Q-ion). For each target compound, Q-ions were monitored in theselected-ion monitoring (SIM) mode. Calibration curves were gen-erated by linear regression of the peak area ratio of analyte to IS atseven concentration levels. Table 1 summarizes the normal con-centration ranges for each analyte. Two additional ions (C-ions)were detected in SIM mode for confirmation purposes (see Results,section 3.1).