Determination of Constituent Sugars and Substitution Pattern

The polymer is hydrolysed to its constituent sugars, the acid hydrolysate reduced to the alditols with NaBH4, the alditols acetylated and then analysed by gas-liquid chromatography (GLC), using a stationary phase that separates 

Distinction between the d and l forms of sugars is made by acid-catalysed formation of glycosides with chiral 2-butanol or 2-octanol the acetylated or trimethylsilylated glycosides with d and l sugars will be diastereomers and thus have different GLC retention times. 

Even today, the resolution of the method is not good and occasional branch points can be missed. This is particularly the case where occasional branch points giving rise to long branches are involved, as with pectin, where they showed up only in the atomic force microscopy of single molecules. Similarly, examination of single molecules of amylose by atomic force microscopy reveals occasional branch points (1 residue in 10 ), well below the resolution of methylation analysis.  

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