| Abstract: | High efficiency liquid chromatography (LC) on both coupled conventional columns and long micro-LC columns, both with diode array detection, has revealed the presence of some hitherto unknown compounds in hop extracts. Proof is advanced that ethanol extracts of hops contain iso-alpha acids. The elution order of the cis-trans pairs of the iso-alpha acids, and the separation of the alpha acids from the deoxyalpha acids, is reversed by switching from methanol to acetonitrile in the reversed phase solvent system. An LC solvent system giving higher resolution (higher selectivity factor) of the iso-alpha acid cis and trans stereoisomers is obtained by adding magnesium salts to the eluent. |
