Determination of alkanes in breath to monitor lipid peroxidation in the presence of volatile toxicants and metabolites

Determination of alkanes in breath of laboratory animals and humans has become a standard-method for monitoring lipid peroxidation in vivo. Isothermal gas chromatography on Porasil C enables sensitive, rapid and repetitive determination of all C₂-C₅-hydrocarbons in breath. Volatile toxicants and metabolites, which would coelute with the alkanes of later injected samples, are deviated by using a precolumn. An automatic switching unit controls withdrawal and injection of samples and backflush of the precolumn in a repetitive manner at fixed intervals. This increases accuracy and sensitivity of analysis and enables virtually unattended operation. The system has been applied for a study on the oxygen-dependance of CCl₄-metabolism in the rat.