Differentiation of the six dimethoxypyrovalerone regioisomers: GC-MS, GC-MS/MS and GC-IR

Publication date: 15 August 2017
Source:Talanta, Volume 171
Author(s): Younis Abiedalla, Jack DeRuiter, Forrest Smith, C. Randall Clark
Multiple and complementary analytical methods are often necessary for the identification of a specific compound from a series of closely related structural isomers. Gas chromatography-mass spectrometry (GC-MS), gas chromatography-product ion mass spectrometry (GC-MS/MS) and gas chromatography-infrared spectroscopy (GC-IR) were used to differentiate between the six dimethoxypyrrovalerone (DMPV) regioisomers. The six regioisomeric aminoketones were separated on a 50% phenyl stationary phase and the elution order is related to the positioning of substituents on the aromatic ring. These six DMPV regioisomers yield essentially identical mass spectral data in both chemical ionization (CI-MS) and electron ionization (EI-MS) spectra as well as identical product ion MS/MS spectra of the iminium cation base peak (m/z 126). These various mass spectral techniques provide data to identify all major structural features of these molecules except the dimethoxy substitution pattern of the aromatic ring. The region of the vapor phase infrared spectra between 1600cm⁻¹ and 1000cm⁻¹ provides a significant number of unique absorption bands characteristic of each individual DMPV regioisomer.

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