Gas chromatography | GC

Learn that gas chromatography is a technique for separating volatile compounds that vaporize easily at room temperature.

Examine the main components: the column (packed or capillary), stationary phase (silicon grease or wax), mobile phase (inert gas like helium), molecular sieve for purification, and detector at the end.

Mix the sample with a volatile solvent such as heptane, acetone, or methanol, then inject it through a septum into the heated injection region kept 20-50°C above the column temperature for rapid vaporization.

Maintain the column at 150-300°C and allow volatile molecules to separate based on their interaction with the stationary and mobile phases, with less volatile compounds moving slowly and more volatile compounds moving fast.

Use a flame ionization detector (FID) that burns hydrogen and oxygen to ionize sample molecules, releasing electrons that are detected as current and amplified by a computer.

Record the chromatogram showing peaks at specific retention times; the area under each peak indicates the concentration of the sample component.

Run known standards (such as methanol and acetone) to establish their retention times, then compare unknown sample peaks to standard peaks to identify present or absent compounds.