How does gas chromatography differ from liquid chromatography?

The primary difference between gas chromatography (GC) and liquid chromatography (LC) lies in the state of the mobile phase used to transport the sample through the system.12

• Mobile Phase: In gas chromatography, an inert gas (such as helium or argon) acts as the mobile phase. In liquid chromatography, a liquid solvent serves this purpose.342
• Sample Requirements: Because GC relies on the sample being carried by a gas stream, it requires the analyte to be vaporized before injection. Consequently, it is best suited for compounds that can be vaporized without decomposing. In contrast, liquid chromatography eliminates the need for vaporization, allowing it to separate a much broader range of substances, including non-volatile or thermally unstable compounds like proteins, amino acids, and inorganic ions.32
• Applications: Due to these differences, LC is often the preferred method for complex biological substances, while GC is highly valued for its speed, resolving power, and sensitivity in analyzing volatile mixtures. Both methods rely on the same fundamental principle: components of a mixture are separated based on their varying affinities for a stationary phase as they are transported through a column.21