Breath analysis and monitoring by membrane extraction with sorbent interface.

An analytical system consisting of a sampling chamber, membrane extraction module, sorbent trap and gas chromatograph with flame ionization or ion mobility detector was used for on-line monitoring of the composition of the last 250 mL portion of human expired breath. The sampling chamber consisted of a tube fitted with check valves on both ends to allow the air to pass through during expiration, but not to return or allow mixing with ambient air. The last portion of breath was held in the chamber at the end of breath expiration. The organic components in the trapped breath were transferred to the carrier gas by permeation through the membrane in the extraction module and were concentrated in the sorbent trap before introduction as a sharp plug on the front of chromatographic column. Moisture in the breath did not penetrate the membrane to a substantial degree. This system was used to investigate presence of acetone as a biologically important marker of human health as well as exposure to volatile compounds.