Application of Extractive Cryogenic Preconcentration with Fourier Transform Infrared Spectroscopy: Preliminary Laboratory Results

摘要

In collaboration with the Jefferson County Department of Health (JCDH) and the Environmental Protection Agency (EPA) Region IV, the University of Alabama in Huntsville (UAHuntsville) developed a nearreal- time trace gas monitor using extractive cryocooled inert preconcentration combined with Fourier transform infrared spectroscopy (ECIP-FTIR). The ECIP-FTIR uses a commercial FTIR spectrometer, a commercial long-path IR gas cell, a commercial acoustic Stirling cyrocooler, and two custom parallel cryogen-free cryotraps to autonomously monitor an evolving multi-pollutant suite of volatile organic compounds (VOCs). Every 15 minutes, the system records a trace gas absorption spectrum and the derived trace gas mixing ratios, using continuous nonpreconcentrated sample flow through the gas cell, to achieve detection limits of ~10 parts per billion by volume (ppbv). Every 4 hours, the FTIR and gas cell obtain similar data on preconcentrated batch samples that have been thermally desorbed from the cryotrap, to improve detection limits to ~50 parts per trillion by volume (pptv). We present initial laboratory data to demonstrate the ECIP-FTIR methodology, which is well suited for a wide range of trace gas research and monitoring applications, including EPA National Air Toxics Trends Stations (NATTS) and National Core monitoring network (NCore).