title: Application of liquid chromatography-nuclear magnetic resonance spectroscopy for the identification of ethyldimethylpyrazine, a food flavouring agent.
abstract: The application of liquid chromatography-nuclear magnetic resonance spectroscopy (LC-NMR) for the direct identification of ethyldimethylpyrazine, a food flavouring agent, has been studied. The commercial product is a mixture of two regio-isomers, 2-ethyl-3,5-dimethylpyrazine (1) and 2-ethyl-3,6-dimethylpyrazine (2); however, the exact composition of the mixture is unknown. Structural characterization by LC-MS and GC-MS was not possible because both regio-isomers yield the same molecular related ion and ion fragmentation. To rapidly identify the two regio-isomers, the product was analyzed by LC-NMR with on-flow and fraction loop modes. From the results, the structure elucidations of the two regio-isomers could be carried out without the need to isolate the isomers by the usual procedures.
authors.affiliation: nsNational Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan. nsugimot@nihs.go.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Sugimoto
authors.forename: Chikako
authors.initials: C
authors.lastname: Yomota
authors.forename: Noriko
authors.initials: N
authors.lastname: Furusho
authors.forename: Kyoko
authors.initials: K
authors.lastname: Sato
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Kenichi
authors.initials: K
authors.lastname: Tanamoto
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D005421:Flavoring Agents / Q000032:analysis*; D005503:Food Additives / Q000032:analysis*; D005504:Food Analysis / Q000379:methods; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010675:Pheromones / Q000032:analysis; D011719:Pyrazines / Q000032:analysis*
chemical_list: D005421:Flavoring Agents; D005503:Food Additives; D010675:Pheromones; D011719:Pyrazines; C504321:2-ethyl-3,6-dimethylpyrazine; C522035:2-ethyl-3,5-dimethylpyrazine