Membrane mass spectrometry for the direct trace analysis of volatile organic compounds in air and water

Very simple membrane inlets can be constructed that are selectively permeable to organic molecules while discriminating against the air or water sample matrix. The membrane thickness directly affects the flow through the membrane such that thinner membranes provide higher throughputs and shorter response times. Higher temperatures result in shortened response times and reduced selectivity of the permeation process. Comparisons of two hollow fiber membrane inlet geometries show that permeation rates are improved in the configuration where the sample flows through the inside of the hollow fiber and the permeating gases are analyzed on the outside, as opposed to the reversed configuration.