Determination of lipid A and endotoxin in serum by mass spectroscopy.

A quantitative technique for determining lipid A content of endotoxin added to serum by combined gas chromatography-mass spectrometry is described. This technique uses detection of the beta-hydroxymyristic acid content of Salmonella minnesota R595 lipopolysaccharide by selected ion monitoring at atomic mass unit of 315.4 The fatty acids produced on hydrolysis of serum containing lipopolysaccharide were extracted and the methyl esters were made. Silica gel chromatography was used to separate methyl esters of hydroxy fatty acids from other fatty acid methyl esters. Trimethylsilyl ether derivatives of the hydroxy fatty acid methyl ester fraction were quantitated by this technique. As little as 200 fmol of beta-hydroxymyristic acid could be detected.