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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Vacuum on the Performance of the Flame Ionization Detector for Vacuum-Outlet Gas Chromatography

Authors
item Bernier, Ulrich
item Bray, Christopher - UF, CHEMISTRY DEPT
item Yost, Richard - UF, CHEMISTRY DEPT

Submitted to: Journal of Microcolumn Separations
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 11, 1999
Publication Date: N/A

Interpretive Summary: The analysis of natural chemicals that attract insect pests, such as mosquitoes to traps, requires highly sophisticated analytical equipment and procedures. Scientists at the USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology and cooperators at the University of Florida, in Gainesville, Florida, have made technical innovations in gas chromatography that enhance the sensitivity and increase the speed of separation, and hence, identification of chemicals of agricultural interest. The equipment that was studied is known as a gas chromatograph equipped with a flame ionization detector. The technical advances in this study will lead to improved methods for chemical analysis.

Technical Abstract: Vacuum-outlet operation of short fused-silica open tubular columns for gas chromatography provides benefits to analysis speed by increasing the optimum velocity while minimizing the loss in resolution. Vacuum-outlet operation of a column with a gas chromatographic detector necessitates that the detector also be under vacuum. Simple modifications to a gas chromatograph/flame ionization detector (GC/FID) system were performed such that vacuum- inlet and vacuum-outlet operation was possible. The vacuum-inlet system was operated in the splitless mode to allow for efficient sample loading prior to operation at reduced pressures. The goal of FID operation at 100 Torr or less was achieved by using oxygen in place of air and optimizing the gas flows under vacuum to maintain a stable flame at pressures as low as 46 Torr. An outlet pressure of 85 Torr with optimized gas flows allowed for routine operation of the FID without solvent-flame out. It was discovered that the sensitivity is enhanced compared to atmospheric operation over a range of outlet pressures from approximately 200 to 400 Torr; however, operation of the FID at the lowest possible pressures decreases the analytical sensitivity due to both the outlet pressure and the absence of helium makeup gas.

Last Modified: 11/25/2014
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