Determination of Higher-carbon Sugars

In undegraded polysaccharides, as well as in mixtures, the presence of a particular type of sugar (aldoheptose, heptulose, and so on) can often be easily demonstrated by a suitable color-reaction. After precise identification of an individual sugar, sometimes achieved by paper chromatography, selected color-reactions may permit its quantitative determination. 

It was found that carbazole and phloroglucinol are unsuitable for determining the heptose content of sugar mixtures because of interference from other sugars similar interference is encountered with resorcinol. With orcinol, cysteine, and diphenylamine, however, specific reactions can be obtained at selected wavelengths. Ketoheptoses (and keto sugars in general) react under milder acid conditions than the aldoses, and this property can be used for identification purposes. In the orcinol test, for 

Order of Separation of Aldoheptoses and Other Sugars on Paper Chromatograms  

D-glycero-irgluco-Heptoae j D-glycero-D-gluco-Heptoae Galactitol ] 

D-pipcero-D-ido-Heptose i -Acetyl-D-gluoosamine j D-Ribose L-Rhamnoae 

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