Pneumatic Focusing Gas Chromotography: A 3-in-1 Continuous, Automated, Ambient-Fenceline-Fugitive Emissions Instrument

VOC Technologies, Inc. (VOCTEC) developed a patent-pending new technology for analysis of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) by compressing an air sample to high pressure before injecting it into a specially designed gas chromatograph (GC). This GC is constructed entirely within a personal computer (the “GC-in-a-PC”), which operates unattended and indefinitely in the field with network communication. Compression both concentrates the sample and removes water vapor by condensation. This procedure is called pneumatic focusing gas chromatography (PFGC). This highly automated new technology has the potential to lower the cost of a VOC/HAP analysis by a factor of 100, requiring no special operator skills. With PFGC, a 300 cc sample can be injected directly on the column and achieve a 50 ppb level of detection (LOD) for benzene, with 500,000 theoretical plates using either flame or photoionization detection. Samples as small as 0.1 cc allow for direct stack monitoring. Because the entire air sample passes the column and detector, ambient methane serves as an internal standard on every analysis. In Phase I, two PFGC instruments were constructed. These instruments were equipped with commercial dual flame and photoionization detectors (FID/PID), and demonstrated their ruggedness, sensitivity, and precision in monitoring Portland’s outdoor air. Monitoring was carried out with one PFGC at an urban monitoring station run by the Oregon Department of Environmental Quality (DEQ). One goal was to compare the performances of the PID and the FID in a TO-14 type environment as conducted on a typical sixth-day canister analysis schedule. The second PFGC, used for laboratory testing and calibration, delivered 1 ppbV precision (standard error in the mean) for sub-ppbV levels of chlorobenzene. In Phase II, VOCTEC will carry out a year-long ambient TO-14 inter-comparison under contract to the DEQ at no cost to the Small Business Innovation Research (SBIR) Program. This will involve DEQ’s traditional U.S. Environmental Protection Agency-approved sixth-day TO-14 canister analysis and VOCTEC’s 24/7 in situ ambient air analysis. Additionally, the TO-14 canisters will be analyzed using PFGC for comparison with the in situ data. In past work, VOCTEC has followed diurnal variation of a major VOC component that was not present when the canister was analyzed. Apparently, this compound either adsorbs or decomposes in the canister. During Phase II, major improvements will be made in chromatographic resolution to better separate HAPs from less toxic VOCs. This will involve novel and proprietary software and hardware modifications of the existing PFGC instrument.