The determination of organic trace gases in the ambient environment at the lower ppb level is demonstrated based on a novel technique combining sorption tube sampling on Molsieve and Carbosieve S-III, thermal desorption, and detection of the trace analyte by hollow waveguide Fourier transform infrared (HWG-FT-IR) spectroscopy. While ethene concentrations of approximately 5 ppm can be directly observed using HWG-FT-IR, enrichment factors of up to 5000 were achieved by sorption tube sampling and thermal desorption. Detection limits of approximately 1 ppb are reported. Efficient enrichment by the sampling tube is achieved due to the favorable internal volume ( approximately 0.4 cm(3) at a length of 470 mm) of the hollow waveguide serving as a miniaturized gas cell. This new method was validated for ethene by thermodesorption-cryofocusing-GC-FID as the reference method. Analytical performance has been compared for standard gas mixtures and for ethene measurements in urban air. Finally, ethene data from a sampling campaign at two alpine sites in Tyrol/Austria are presented.
A gas sensor for application in water analysis was developed by combination of a mid-infrared (MIR) hollow waveguide with a Fourier transform infrared (FT-IR) spectrometer and coupling of the hollow waveguide gas sensor module to a supported capillary membrane sampler (SCMS) for continuous liquid-gas extraction. Different hollow waveguides have been characterized in this study for developing an optimized optical configuration. Analysis of industrially relevant compounds has been performed, investigating chlorinated hydrocarbons (CHCs), such as dichloromethane and chloroform, representing highly volatile analytes, and 1,4-dioxane as an example of target compounds with low volatility. The suitability of this spectroscopic IR sensing system for industrial applications is demonstrated under simulated real-world conditions with limits of detection in the ppb (v/v) and ppm (v/v) concentration range for CHCs and 1,4-dioxane, respectively.
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