ABSTRACT Dielectric barrier discharge ioniziation (DBDI) is an ambient ionization technique that enables real‐time, in situ analysis of for example, volatile compounds such as terpenes. Terpenes pose an analytical challenge due to isomerism and shared structural features, often leading to similar or identical MS spectra, which complicates structural annotation. DBDI is a low‐temperature plasma that generates reagent ions that ionize analytes via multiple pathways. The reagent‐ion composition, and thus the presence and distribution of adducts and precursor ions, depends on the ionization atmosphere inside of the source and can be tuned by adjusting for example, humidity or dopant gases. Here, DBDI‐MS was used to acquire spectra of six terpenes under varied atmospheres (humidified air, MeOH, N 2 ) and these were compared with electron‐ionization (EI) mass spectra, the gold standard for terpene analysis. Isomeric pairs that are not distinguishable by EI (α/ß‐pinene and borneol/isoborneol) produced distinct DBDI‐MS patterns. DBDI‐MS therefore enables isomer differentiation without chromatographic separation and complements EI for structure elucidation by providing structure‐ and isomer‐dependent spectral fingerprints.
Raeber et al. (Sat,) studied this question.