67] Quantitative trace analysis of volatile organic compounds

Abstract

Publisher Summary This chapter describes a procedure that can be used for structural elucidations, as well as for physiological and biochemical studies of the volatile organic compounds (VOC) which are needed for quantitative analyses. Closed culture systems which restrict gas exchange are preferred for quantitative studies on VOC. This applies both to fermenters and shaking cultures. Shaking cultures are best performed in 300-ml Erlenmeyer flasks with ground glass joints and are inoculated with 100 ml of cyanobacterial suspension. When fermenter cultures are used for experiments, highly volatile substances (e.g., isopropylthiol) can be trapped at the exit port of the aeration gas. The VOC cartridge described can easily be fastened to the exit of the fermenter with its ground glass joint. When aliquots are removed from the cyanobacterial suspension for analysis of less volatile compounds, the samples should be as small as possible (10-20 ml of a 2-liter fermenter) to keep the changes of the proportion of the gas to liquid phase in the vessel as small as possible. To reduce any loss of VOC by the aeration gas stream, the latter should be reduced to low flow rates in combination with increased CO 2 concentrations.