Gas chromatography-mass spectrometry of lipopolysaccharide 3-hydroxy fatty acids: comparison of pentafluorobenzoyl and trimethylsilyl methyl ester derivatives

Abstract

3-Hydroxytetradecanoic and 3-hydroxyhexadecanoic acids were used as chemical markers for the determination of lipopolysaccharides by gas chromatography-mass spectrometry of their pentafluorobenzoyl and trimethylsilyl methyl ester derivatives. The latter derivatives were simpler to prepare than the former, although both were chemically stable. Analysis of pentafluorobenzoyl derivatives (chemical ionization mode with negative ion detection) provided somewhat better sensitivity than analysis of trimethylsilyl derivatives (electron impact mode): 1 pg (injected amount) of pentafluorobenzoyl derivatives was detectable under routine conditions. Both types of derivative gave similar values when used to measure lipopolysaccharides in a bacteria-contaminated pharmacological product. The described methods are useful for the determination and characterization of lipopolysaccharides in various environments.