GAS-CHROMATOGRAPHY MASS-SPECTROMETRY METHODS FOR THE ANALYSIS OF MYCOCEROSIC ACIDS PRESENT IN MYCOBACTERIUM-TUBERCULOSIS

Mycocerosic acids of Mycobacterium tuberculosis were studied by gas ch romatography-mass spectrometry. Mycobacterial cells were subjected to alkaline hydrolysis and then acidified before being extracted using pe troleum ether to collect the acids. Methyl ester, trimethylsilyl and p entafluorobenzyl derivatives of the mycocerosic acids were formed. In the electron impact mode, using selected-ion monitoring, the methyl es ter derivative of 2,4,6,8-tetramethyloctacosanoic acid (C-32 mycoceros ic acid) was detectable down to 20 pg (injected amount), whereas in th e negative-ion chemical ionization mode, the pentafluorobenzyl derivat ive was detectable down to 2 pg, provided that the temperature of the ion source was at least 240 degrees C. The described methods can be us ed to demonstrate and quantify certain species of Mycobacterium, inclu ding M. tuberculosis, in clinical or environmental samples. (C) 1998 E lsevier Science B.V.