Gas chromatography–mass spectrometry methods for the analysis of mycocerosic acids present in Mycobacterium tuberculosis

Mycocerosic acids of Mycobacterium tuberculosis were studied by gas chromatography–mass spectrometry. Mycobacterial cells were subjected to alkaline hydrolysis and then acidified before being extracted using petroleum ether to collect the acids. Methyl ester, trimethylsilyl and pentafluorobenzyl derivatives of the mycocerosic acids were formed. In the electron impact mode, using selected-ion monitoring, the methyl ester derivative of 2,4,6,8-tetramethyloctacosanoic acid (C mycocerosic acid) was detectable down to 20 pg (injected amount), whereas in the negative-ion chemical ionization 32 mode, the pentafluorobenzyl derivative was detectable down to 2 pg, provided that the temperature of the ion source was at least 2408C. The described methods can be used to demonstrate and quantify certain species of Mycobacterium, including M. tuberculosis, in clinical or environmental samples.  1998 Elsevier Science B.V.