Simultaneous determination of fluoxetine and norfluoxetine enantiomers using isotope discrimination mass spectroscopy solution method and its application in the CYP2C9-mediated stereoselective interactions

► An isotope discrimination MS solution method was developed for chiral separation. ► Separated on column or not is not affect the enantiomers determination. ► The method has high throughput and high sensitivity. ► No significant kinetic isotope effect was found to the S-fluoxetine-d5 metabolism.