High surface area membrane introduction mass spectrometry for analysis of volatile and semi-volatile organic compounds in air

The construction, optimization, and testing of a novel geometry for a semi-permeable polydimethylsiloxane membrane introduction mass spectrometry (MIMS) system is described. A long poly(dimethylsiloxane) capillary membrane (0.30 mm i.d., 0.64 mm o.d., 60 cm long) was positioned coaxially inside polytetrafluoroethylene tubing (0.80 mm i.d. and 1.60 mm o.d.), allowing for a large surface area membrane of relatively small thickness. Helium, flowing counter-current on the vacuum side of the membrane, swept the permeate into the mass spectrometer. This optimized geometry for permeation MIMS air analysis allows on-line detection of volatile and semi-volatile organic compounds of environmental interest, with limits of detection in the ppt range and a linear response over 3 to 4 orders of magnitude. The system is characterized by short rise and fall times, 10 and 48 s, respectively, for toluene. Copyright (C) 2001 John Wiley & Sons, Ltd.