Quantitation of Vaporized γ-Aminobutyric Acid in Cigarette Smoke Extract From e-Cigarettes by the Combination of HPLC-Fluorescence Detection and Derivatization With DBD-F

Gamma-aminobutyric acid (GABA), which has attracted much attention as a bioactive ingredient, is used in functional foods. Recently, electronic cigarette (e-cigarette) products for inhaling vaporized GABA have become commercially available. In this study, we developed a high-performance liquid chromatography–fluorescence method for detecting GABA derivatized with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F) in cigarette smoke extract (CSE). The vaporized GABA captured in CSE was derivatized with DBD-F under moderate conditions (80°C, 30 min). After chromatographic separation, the DBD-GABA derivative was detected at 437 and 558 nm. The calibration curve of GABA ranging from 10 to 20,000 ng/mL showed good linearity (more than 0.999). The limit of detection at a signal-to-noise ratio of 3 was 1.1 ng/mL. The method was applied to the detection of GABA in e-liquid and CSE for two kinds of e-cigarette products, and the estimated collection efficiency of GABA was approximately 25%. Furthermore, the detection of minor components, such as glutamine, glutamic acid, and arginine, in the e-liquid proved that the GABA used in the e-cigarette was prepared by microbial fermentation.