Abstract: A system and method of measuring volatile and semi-volatile reduced organic compound content and volatile and semi-volatile oxidized organic compound content in a sample, using a dual detection system is provided. The method comprises introducing the sample into a semi-permeable membrane introduction interface, sweeping permeate from the membrane introduction interface with a sweep gas, splitting the permeate into a first stream and a second stream, essentially simultaneously detecting volatile and semi-volatile reduced organic compounds and oxidized and semi-volatile organic compounds with a flame ionization detector and an electron capture detector, and computing differences in detector signals, thereby measuring volatile and semi-volatile reduced organic content and volatile and semi-volatile oxidized organic compound content in the sample.

Abstract: A membrane introduction mass spectrometry (MIMS) sampling interface is presented that demonstrates improved online performance for the direct, real-time measurement of semi-volatile organic compounds (SVOCs) in samples such as air and water, at parts-per-billion and parts-per-trillion levels. The device is based upon a capillary hollow fiber silicone (polydimethylsiloxane) membrane in a ‘flow-over’ configuration that is resistively heated on the membrane interior. One embodiment resistively heats using a coaxial nichrome wire, establishing a thermal gradient counter to the analyte concentration gradient. This arrangement allows for continuous and/or pulsed heating modes, affording excellent sensitivity for the online measurement of SVOCs while retaining sensitivity for volatile organic compounds (VOCs). In addition, the signal response time for SVOCs is reduced substantially over conventional MIMS methods.