Analysis of amines and other bacterial products by head-space gas chromatography

A gas chromatographic (GC) head-space technique is presented, which is suitable for the analysis of volatile products in bacterial broth cultures. This is exemplified by studies on Clostridium septicum, Klebsiella pneumoniae and Proteus mirabilis. The media were acidified or made alkaline and after heating, samples of the gas phase above the media were directly injected into the gas chromatograph. A gas chromatograph equipped with dual columns and flame ionization detectors was used, employing Porapak Q and Chromosorb 103 as stationary phases. Analysis of acidified media, using Porapak Q, gave chromatograms representing acidic and neutral volatile products, while when analysing samples made alkaline, using Chromosorb 103, alkaline and neutral compounds could be detected. Interest was particularly concentrated on the analysis of bacterial amines. P. mirabilis was found to produce isobutylamine and isopentylamine, which were identified by mass spectrometry and GC retention times C. septicum produced ethylamine. The GC head-space technique described constitutes a means for rapid identification of microorganisms. It is adaptable for use on a routine basis in the clinical microbiological laboratory.