Sucrose is a disaccharide, which is composed, of a glucose molecule and a fructose molecule linked by glycosidic bond. The figure below shows a 1H NMR Spectrum of sucrose, 13C NMR Spectrum of sucrose Mass Spectrum of sucrose: The structures of alpha and beta glucose molecules are as follows: Alpha and beta glucoses are isomers, they have the same chemical formula but different in chemical structures. The major difference between the isomers is the direction of hydrogen group and hydroxyl groups at carbon 1. From the structure shown above, we can see that the hydroxyl group of alpha glucose is pointing downwards and that of beta glucose is pointing upwards.
It is difficult to isolate different sugars because there can be many kinds of sugars isomers and there is no chromophore for sugars. Also, compare to other natural product, sugars have high sensitivity of the surrounding environment such as temperature and humidity, the chemical properties of sugars will change according to the surrounding environment. Thus, it is very difficult to isolate sugars. For example, glucose has a chemical formula of C6H12O6 , with the same chemical formula, there can be 16 isomers of aldohexoses as follows, each of it representing a different sugar. Since all the sugar isomers are having the same chemical formula and functional groups, they have similar chemical properties so isolation of sugars is difficult.
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This detection method is based on the difference in refractive index of sugars sample to the mobile phase of the HPLC column. The use of HPLC detection of sugars can down to the nano-mole, however there is limitation for using this method to detect sugars as it can only detect monosaccharaides and disaccharides but not the