Chemistry
Gas Chromatography (GC)
Definition: Gas chromatography is a physical method of separation in which the components to be separated are distributed between two phases, one being a stationary bed of large surface area, and the other a gas that percolates through the stationary bed. When the stationary phase is a solid, the separation process is more precisely called gas-solid chromatography.
Introduction: Gas Chromatography is a technique widely used to separate complex mixtures of substances. Compounds present in a volatile liquid or gaseous solute are isolated after traveling through a coated column based on the substance’s size and intermolecular interactions. If a compound tends to bind to the column through intermolecular interactions, it takes a longer time to emerge compared with a compound that does not tend to stick onto the column. The level of binding experienced between the substances and the column is determined based on the number and strength of intermolecular interactions between the two species. Substances that pass quickly through the column exhibit fewer intermolecular interactions with the column.
The Vernier Mini GC uses a metal column with a nonpolar coating, called the stationary phase. A sample, consisting of one or more compounds, is injected into the column and is carried through the stationary phase by atmospheric air, which acts as the mobile phase. The nonpolar coating of the stationary phase most strongly retains solutes of the same polarity. Organic compounds flowing out of the chromatography column are then detected by a chemical sensor that produces electrical responses proportional to the concentration of the compounds. The presence of such a chemical at the detector is seen as a peak on a chromatogram. The unique time it takes for a compound to exit the column after it is injected is called the retention time. With a gas chromatograph, a compound can be identified from a mixture by its retention time.
Several factors can
Definition: Gas chromatography is a physical method of separation in which the components to be separated are distributed between two phases, one being a stationary bed of large surface area, and the other a gas that percolates through the stationary bed. When the stationary phase is a solid, the separation process is more precisely called gas-solid chromatography.
Introduction: Gas Chromatography is a technique widely used to separate complex mixtures of substances. Compounds present in a volatile liquid or gaseous solute are isolated after traveling through a coated column based on the substance’s size and intermolecular interactions. If a compound tends to bind to the column through intermolecular interactions, it takes a longer time to emerge compared with a compound that does not tend to stick onto the column. The level of binding experienced between the substances and the column is determined based on the number and strength of intermolecular interactions between the two species. Substances that pass quickly through the column exhibit fewer intermolecular interactions with the column.
The Vernier Mini GC uses a metal column with a nonpolar coating, called the stationary phase. A sample, consisting of one or more compounds, is injected into the column and is carried through the stationary phase by atmospheric air, which acts as the mobile phase. The nonpolar coating of the stationary phase most strongly retains solutes of the same polarity. Organic compounds flowing out of the chromatography column are then detected by a chemical sensor that produces electrical responses proportional to the concentration of the compounds. The presence of such a chemical at the detector is seen as a peak on a chromatogram. The unique time it takes for a compound to exit the column after it is injected is called the retention time. With a gas chromatograph, a compound can be identified from a mixture by its retention time.
Several factors can
References: 1. Skoog, D. A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis. Sixth Edition, Thomson Brooks/Cole, USA, 2007. 2. Krugers, J. Instrumentation in Gas Chromatography. Centrex Publishing Company-Eindhoven, Netherlands, 1968. 3. Hubschmann, H. Handbook of GC/MS: Fundamentals and Applications. Wiley-VCH Verlag, Germany, 2001. 4. Scott, R. P. W. Chromatographic Detectors: Design, Function, and Operation. Marcel Dekker, Inc., USA, 1996. 5. J.N. Driscoll. REview of Photoionization Detection in Gas Chromatography: The first Decade. Journal of CHromatographic Science , Vol 23. November 1985. 488-492. 6. Boer, H. , "Vapour phase Chromatography", ed. Desty, D. H., 169 (Butterworths Sci. Pub., London, 1957). 7. Dimbat, M. , Porter, P. E. , and Stross, F. H. , Anal. Chem., 28, 290 (1956). | Article | ISI | ChemPort | Appendix