Improved quantification of γ-aminobutyric acid in rice using stable isotope dilution gas chromatography-mass spectrometry

An accurate method for the analysis of γ-aminobutyric acid (GABA) in rice grain was developed using trimethylsilyl (TMS) derivatization and stable isotope dilution gas chromatography-mass spectrometry. When this method was used with GABA‑d6 as an internal standard (IS), the observed GABA concentration was maintained at 100% of the initial concentration with increasing storage time of the vial in the autosampler. In contrast, when using ribitol as an IS and multiple injections from one vial or single injections from different vials, the observed GABA concentration was 85 and 113% of the initial concentration upon increased storage time, respectively. The improved method recoveries at two different spike levels were between 93.3 and 97.8%, with relative standard deviations of less than 3.3%. The GABA content of resveratrol-enriched transgenic rice was compared with that of its non-transgenic counterpart from two field sites, and statistically non-significant differences were observed between the two grains.