Gas chromatography

Gas chromatography separates vaporized compounds as a carrier gas moves them through a column. Compounds emerge at different times because they interact differently with the column’s stationary phase.

Carrier gas: An inert gas that transports vaporized sample components through a chromatographic column. Its flow carries analytes through the column and affects their travel times.
Chromatography: A family of separation methods that distribute mixture components differently between a mobile phase and a stationary phase. Gas chromatography is one member of this broader family of separation techniques.
Volatile organic compounds: Carbon-containing compounds that readily evaporate under ordinary environmental or laboratory conditions. Their volatility makes them common targets for gas chromatographic analysis.
Liquid chromatography: A separation technique in which a liquid mobile phase carries compounds through a stationary phase. It can analyze compounds that are insufficiently volatile or thermally unstable for gas chromatography.
Gas chromatography column: A tube containing a stationary phase, where gas chromatography separates sample components. Its dimensions and stationary phase determine how compounds separate.
Stationary phase: The phase held in place in chromatography that interacts with compounds carried by the mobile phase. Differences in analyte affinity for this phase produce separation.
Headspace analysis: A sampling method that analyzes vapor above a liquid or solid rather than injecting the whole sample. It introduces volatile components while limiting nonvolatile matrix material.
High-performance liquid chromatography: Liquid chromatography that uses high pressure to pass solvent through a packed column efficiently. It handles many nonvolatile analytes that cannot be vaporized for gas chromatography.
Retention time: The time between sample injection and a compound’s detection in chromatography. Different retention times reveal when separated compounds leave the column.
Mobile phase: The fluid that moves sample components through a chromatographic system. In gas chromatography, the mobile phase is a flowing carrier gas.

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