Quantitative analysis of carbohydrate residues of glycoproteins and glycolipids by gas—liquid chromatography : An appraisal of experimental details

Abstract

Many investigators have reported problems with the use of d-mannitol and other alditos as internal standards for gas chromatographic quantification of trimethylsilyl ether derivatives of methyl glycosides. Quantification of carbohydrate residues of glycoproteins and glycolipids requires neutralization of the products of dry acidic methanolysis. Silver carbonate and Amberlite IR-45 ion exchange resin (OH −) were compared as neutralization agents for 0.75 N HCL methanolysates (80°, 20 h). Only 4/2-17% of the d-mannitol internal standard was recovered when a 50 nmole equimolar mixture of d-mannitol and α-methyl glycosides was neutralized with silver carbonate. Addition of 0.1 ml of acetic anhydride or glacial acetic acid after silver carbonate neutralization did not prevent significant loss of d-mannitol, myo- inositol and perseitol at the 50 nmole level. There was no appreciable loss of d-mannitol internal standard, when compared to α-methyl glycosides, after IR-45 resin (OH −) neutralization. Resin neutralization allowed 10/2-200 nmoles of d-mannitol internal standard to be added to acidic methanolysates immediately after methanolysis and carried directly through the analytical procedure.