Technique for gas-chromatographic measurement of volatile alkanes from single-breath samples

For detection of small quantities of alkanes that are present in expired breath, these gases have hitherto been concentrated, either by passing large volumes of breath through a liquid-nitrogen-cooled precolumn or by use of a closed collection system. Here, we describe a technique for analyzing small volumes of gas from single-breath samples from humans, in which no precolumn is required. Results are linearly related to sample concentrations of ethane, propane, butane, and pentane in the range 0 to 13 nmol per liter of air (r = 0.999). Within-run coefficients of variation were less than 15%. Breath samples could be stored for as long as 10 h without loss of the alkanes. We also report alkane concentrations in samples of alveolar gas and total breath collected from normal subjects. This technique appears to be well suited for measuring alkane concentrations in single-breath samples.