9-Fluorenylmethyl chloroformate as a fluorescence-labeling reagent for derivatization of carboxylic acid moiety of sodium valproate using liquid chromatography/tandem mass spectrometry for binding characterization: A human pharmacokinetic study

► FMOC-Cl is a suitable labeling agent for derivatization of chemicals amines or hydroxyl groups. ► The reagent was applied in labeling of valproate (VPA) an anticonvulsant with carboxylic acid moiety. ► To document reaction between FMOC-Cl and carboxylic acid moiety a LC-MS/MS method was developed. ► The method is simple, rapid, sensitive which needs using lower sample volume. ► Potential application of FMOC in assay of carboxylic acids, makes our method attractive.