Derivatization of Carbohydrate Chains

Despite the development of ESI and MALDI modes of ionization, GC/MS is still a popular method for determination of the monosaccharide composition of carbohydrate chains [13]. This method involves breaking the oligosaccharide into constituent monosaccharides by hydrolysis or methanolysis. Following derivatization, the released monosaccharides are analyzed by GC/MS to identify sugar residues through their retention times and mass spectral profile. Common derivatization procedures are methylation, acetylation, and trimethylsilylation. 

A GC/MS method, commonly called linkage analysis or methylation analysis, has also proven to be a successful approach to determining interresidue linkage and branch points [14]. It involves complete alkylation of all free hydroxyl groups. The fully methylated oligosaccharides are hydrolyzed into monomers, which are further reduced and acetylated to provide partially methylated alditol acetates (PAMAs). Acetylation takes place at those positions that were newly exposed by hydrolysis and reduction. The GC retention times and fragmentation patterns can reveal the mode of attachment in the native sugar. 

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