Sugars mixtures, separation

Fig. 1 Schematic diagram of the chromatographic separation (A) and the fluorescence scan (B) of a sugar mixture containing 1 pg substance per chromatogram zone. Lactose (1), fructose (2), arabinose (3), xylose (4), rhamnose (5), mixture (G).

Only model studies have so far been reported, and the method has not yet been applied to the analysis of sugar mixtures, with the exceptions noted.48,49 The recovery of glucose-14C trifluoroacetate from a column of Carbowax 20 M or SF-96 has been shown to be 5 to 14% and 3 to 5%, respectively.208 Table III (p. 112) records further details of the separation of sugars and their derivatives as trifluoroacetates. 

Interaction of solvent with sugars being separated is typified by the lactone-uronic acid interconversion which may take place during chromatography in collidine mixtures.27 Moore and Stein have shown that acidic amino acids, in an acidic 1-butanol solvent on starch columns, are esterified to the extent of 6 to 7 % during chromatography.63... 

Which separation method should be used to separate a water - sugar mixture ... 

One characteristic of a mixture is that it can be separated into its components by physical processes. The word physical means that the process does not change the chemical identity of a substance. How could you separate a sand/sugar mixture into pure sand and pure sucrose The simplest physical means would be to look at it with a microscope and separate the bits of sugar and sand with tweezers. You are right in thinking that there must be an easier way. 

Stroh914 has reviewed the influence of substituents on the reaction of phenylhydrazines with sugars and their selectivity in reaction with sugar mixtures. The so-called diphenyl-methanedimethylhydrazine [p,p/-methylenedi(Arl-methylphenylhydrazine)], for instance, is sometimes useful for separating sugar mixtures as it condenses more easily with most aldoses than with ketoses.915 1-Methyl-1-phenylhydrazine can also be used to differentiate aldoses from ketoses with aldoses it forms the hydrazone but with ketoses the osazone.916... 

Several laboratories routinely use alditol acetate derivatives for analyzing sugar mixtures by g.l.c. in combination with m.s. The usefulness of the method is illustrated by the following examples. Sugar analyses of lipopolysaccharides from Salmonella species have demonstrated that several chemotypes contain 3,6-dideoxyhexoses. When these sugars are converted into alditol acetates, the isomers can be separated by g.l.c., and their identity as 3,6-dideoxyhexoses can be established by... 

Thin-layer chromatography affords a simple, rapid and sensitive method for the qualitative and quantitative analysis of low molecular weight sugars and their derivatives. In the few years since Stahl and ELaltenbach [1] extended TLC to the separation of sugar mixtures, the method has been adopted for a wide spectrum of analytical problems. This chapter considers two classes of compounds the hydrophilic carbohydrates and their derivatives which are hydrophobic in nature. 

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