Double-membrane sampling system in a mass spectrometer for the study of exhaled air

A double-membrane sample-introduction system is described that enables mass spectrometric determination of volatile organic compounds in air, while ensuring their detection limits are as low as a few fractions of ppb of sample composition in real time with a response delay from a few seconds to a few dozens of seconds. It includes two membrane interfaces separated by a volume, the gas pressure in which is maintained through a channel with an adjustable evacuation cross-section. The results of numerical simulation and experimental testing of the system are provided. A technique for selecting and calculating system parameters is described. The possibility of using this system for diagnosing diseases by trace amounts of biomarkers in exhaled air is discussed.