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Anal Chem

Title:		"Compact, Automated, Inexpensive, and Field-Deployable Vacuum-Outlet Gas Chromatograph for Trace-Concentration Gas-Phase Organic Compounds"
Author(s):		Skog KM; Xiong F; Kawashima H; Doyle E; Soto R; Gentner DR;
Address:		"Department of Chemical & Environmental Engineering, School of Engineering and Applied Science , Yale University , New Haven , Connecticut 06511 , United States. SEARCH (Solutions for Energy, Air, Climate and Health) Center , Yale University , New Haven , Connecticut 06511 , United States"
Journal Title:		Anal Chem
Year:		2019
Volume:		20190103
Issue:		2
Page Number:		1318 - 1327
DOI:		10.1021/acs.analchem.8b03095
ISSN/ISBN:		1520-6882 (Electronic) 0003-2700 (Linking)
Abstract:		"The identification and quantification of gas-phase organic compounds, such as volatile organic compounds (VOCs), frequently use gas chromatography (GC), which typically requires high-purity compressed gases. We have developed a new instrument for trace-concentration measurements of VOCs and intermediate-volatility compounds of up to 14 carbon atoms in a fully automated (computer-free), independent, low-cost, compact GC-based system for the quantitative analysis of complex mixtures without the need for compressed, high-purity gases or expensive detectors. Through adsorptive analyte preconcentration, vacuum GC, photoionization detectors, and need-based water-vapor control, we enable sensitive and selective measurements with picogram-level limits of detection (i.e., under 15 ppt in a 4 L sample for most compounds). We validate performance against a commercial pressurized GC, including resolving challenging isomers of similar volatility, such as ethylbenzene and m/ p-xylene. We employ vacuum GC across the whole column with filtered air as a carrier gas, producing long-term system stability and performance over a wide range of analytes. Through theory and experiments, we present variations in analyte diffusivities in the mobile phase, analyte elution temperatures, optimal linear velocities, and separation-plate heights with vacuum GC in air at different pressures, and we optimize our instrument to exploit these differences. At 2-6 psia, the molecular diffusion coefficients are 6.4-2.1 times larger and the elution temperatures are 39-92 degrees C lower than with pressurized GC with helium (at 30 psig) depending on the molecular structure, and we find a wide range of optimal linear velocities (up to 60 cm s(-1)) that are faster with broader tolerances than with pressurized-N(2) GC"
Keywords:
Notes:		"PubMed-not-MEDLINESkog, Kate M Xiong, Fulizi Kawashima, Hitoshi Doyle, Evan Soto, Ricardo Gentner, Drew R eng Research Support, Non-U.S. Gov't 2019/01/04 Anal Chem. 2019 Jan 15; 91(2):1318-1327. doi: 10.1021/acs.analchem.8b03095. Epub 2019 Jan 3"