Sodium triacetoxyborohydride (STAB) is a mild, selective, and frequently used reducing agent for reductive amination transformations. STAB has been reported to undergo degradation when exposed to air, often requiring additional sub-stoichiometric reagent charges to drive reactions to completion. We report the development and qualification of a rapid, quantitative GC derivatization method using 3,4-dihydroisoquinoline to enable accurate hydride assay determination of STAB. Assay data generated from this method has been directly compared to a recently published HPLC method using bromosalicaldehyde as the derivatization reagent. The degradation kinetics of STAB have also been further investigated by Raman spectroscopy to demonstrate how exposure of STAB to air can negatively impact the reagent’s performance.