Enantioselective analysis of ketoprofen in human saliva by liquid chromatography/tandem mass spectrometry with chiral derivatization

The enantioselective analytical method for trace ketoprofen (KET) in human saliva was developed for the first time using liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) combined with a derivatization using a chiral reagent, (S)‑1‑methyl‑4‑(5‑(3‑aminopyrrolidin‑1‑yl)‑2,4‑dinitro‑phenyl)piperazine (APy‑PPZ). The APy‑PPZ derivatization enabled highly sensitive detection (detection limit, 0.5 fmol on column) and complete separation with high resolution (Rs = 4.3) of KET enantiomers. The calibration curves of both KET enantiomers in saliva were linear in the concentration range of 5-500 nM. The developed method showed good analytical performance with relative standard deviations (RSDs) below 2.6% and good accuracy (100.5-105.9%) through intra- and inter-assay and gave a potential for practical application to the quantitative determination of KET in human saliva.