Analysis of lipopolysaccharides by methanolysis, trifluoroacetylation, and gas chromatography on a fused-silica capillary column

A gas chromatographic method for simultaneous analysis of fatty acids and sugars of lipopolysaccharides (LPS) has been developed. The sample (1 mg or less) is methanolyzed at 85°C overnight in 2 M HCl in methanol. The released methyl esters and methyl glycosides are trifluoroacetylated and chromatographed on a methylsilicone-impregnated fused-silica capillary column. This column resolves all ordinary LPS sugars and fatty acids, and quantitative analysis is possible, including 2-deto-3-deoxyoctanoic acid (KDO), glucosamine and heptoses. 3,6-Dideoxyhexoses show some thermal degradation at 85°C during methanolysis, but this can be overcome by lowering the temperature to 37°C. For KDO the higher temperature similarly causes some degradation, but a reproducile response factor was found. The method appears to be useful for analysis of purified LPS as well as a means for monitoring for LPS content during purification of bacterial antigents of different kinds.