Advanced Topic 907 of 1102 Analytical, Lab & Spectroscopy
Gas Chromatography
Volatile compounds separated by passage through a heated column with gas carrier.
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In-depth explanation of Gas Chromatography
Gas chromatography separates volatile compounds by vaporizing the sample, carrying it in an inert gas such as helium or nitrogen through a long heated column coated with a liquid or polymer stationary phase. Components separate by their boiling points and their interactions with the stationary phase, and they elute at characteristic retention times. The most common detector is a flame ionization detector, which responds to organic compounds, while coupling to a mass spectrometer identifies the eluting species. Column temperature is often programmed to rise during the run so that high-boiling compounds elute in a reasonable time. Gas chromatography suits volatile and thermally stable compounds and is widely used in environmental, forensic and petroleum analysis.
Going deeper: Gas Chromatography
Key ideas: Retention time depends on boiling point and column polarity. Use a nonpolar column to separate by boiling point and a polar column to separate by polarity. Quantify with peak area and an internal standard to correct for injection variation. Resolution R = 2 (t2 minus t1)/(w1 + w2), with R of 1.5 giving baseline separation. Typical carrier gas flow is 1 to 2 mL/min for capillary columns.
Common mistakes and connections: Injecting nonvolatile or thermally unstable samples fouls the inlet and column. Students assume peak height always equals amount, but area is more reliable when peaks broaden. Water in a sample damages some columns. Derivatization makes polar compounds volatile. Related to mass spectrometry (GC-MS), boiling points, retention time and HPLC.
Visualization of Gas Chromatography
A headspace chromatogram for blood alcohol: methanol, ethanol, acetone and isopropanol elute in order of volatility, with an internal standard at the end. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Blood alcohol is measured by headspace gas chromatography with a flame ionization detector.
Frequently asked questions about Gas Chromatography
What is Gas Chromatography?
Volatile compounds separated by passage through a heated column with gas carrier.
Is Gas Chromatography a beginner, intermediate or advanced topic?
Gas Chromatography is a advanced topic in Analytical, Lab & Spectroscopy. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Gas Chromatography?
Study these earlier topics in Analytical, Lab & Spectroscopy first: Paper Chromatography, Thin Layer Chromatography, Column Chromatography.
What comes after Gas Chromatography?
The next topics in Analytical, Lab & Spectroscopy are HPLC and Retention Time.
Can I practise Gas Chromatography with quizzes?
Yes. The interactive lesson includes a self-check question on Gas Chromatography, and the Analytical, Lab & Spectroscopy quiz draws on every topic in this area.
Where Gas Chromatography fits in Analytical, Lab & Spectroscopy
Gas Chromatography is topic 31 of 99 in Analytical, Lab & Spectroscopy.