Application of 4-Diethylaminobenzoic Acid <i>N</i>-Succinimidyl Ester and Its Deuterated Isotopologue as Derivatization Reagents to Quantitative Analysis of γ-Aminobutyric Acid in Serum by LC/ESI-MS/MS

γ-Aminobutyric acid (GABA) is an inhibitory neurotransmitter having anti-anxiety, stress-reducing and sleep-enhancing effects. The blood GABA concentration has the potential to become a diagnostic index for depression schizophrenia. In this study, we developed method quantification of in human serum by liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) combined with derivatization using pair reagents, 4-diethylaminobenzoic N-succinimidyl ester (DEABAS) its deuterated isotopologue (dDEABAS). deproteinized samples were derivatized DEABAS, which dDEABAS-derivatized standard known amount was then added. DEABAS-derivatization enhanced not only ESI-MS/MS sensitivity but also LC retention, enabled separation from interfering isomers. Satisfactory assay precision accuracy acquired adding GABA, served as internal worked well correcting matrix effect instrument drift. had satisfactory applicability real sample analysis because it successfully used quantify healthy subjects.