Gas chromatographic retention of carbohydrate trimethylsilyl ethers : III. Ketohexoses

Abstract Five tautomeric forms, four cyclic and one acyclic, of the four ketohexoses (fructose, sorbose, tagatose and psicose) were separated as their O-trimethylsilyl (TMS) ethers by gas chromatography on several capillary columns, and identified by gas chromatography - mass spectrometry. The retention indices changed slightly with temperature. As with aldoses, their chromatographic behaviour was different from that of other ethers. Principal component analysis showed the specific behaviour of some phases towards some compound groups. A mathematical approach developed for aldoses was applied to ketohexose retention indices in order to relate them to their structural characteristics. The results were similar to those found for aldoses, except for pyranose forms, where equatorial OTMS groups seemed to have a negative effect on the retention.