Gas Chromatography (GC)


Introduction

Gas chromatography is a chromatographic technique that can be used to separate volatile organic compounds. A gas chromatograph consists of a flowing mobile phase, an injection port, a separation column containing the stationary phase, and a detector. The organic compounds are separated due to differences in their partitioning behavior between the mobile gas phase and the stationary phase in the column.


Instrumentation

Mobile phases are generally inert gases such as helium, argon, or nitrogen. The injection port consists of a rubber septum through which a syringe needle is inserted to inject the sample. The injection port is maintained at a higher temperture than the boiling point of the least volatile component in the sample mixture. Since the partitioning behavior is dependant on temperture, the separation column is usually contained in a thermostat-controlled oven. Separating components with a wide range of boiling points is accomplished by starting at a low oven temperture and increasing the temperture over time to elute the high-boiling point components. Most columns contain a liquid stationary phase on a solid support. Separation of low-molecular weight gases is accomplished with solid adsorbents. Separate documents describe some specific GC Columns and GC Detectors.

Schematic of a gas chromatograph

Pictures of some gas chromatographs


Further Information


Science Hypermedia Home Page

Copyright © 1996 by Brian M. Tissue

/chem-ed/sep/gc/gc.htm, updated 6/13/96