gaschromatografi

Gas chromatography (GC) is a separation technique used to analyze volatile and semi-volatile compounds in a mixture. It separates components based on their interactions with a stationary phase inside a chromatographic column as a mobile phase, typically an inert carrier gas. Compounds with greater affinity for the stationary phase move more slowly and elute later than those with weaker interactions.

In a GC instrument, a sample is vaporized and carried by a heated injection port through a column housed in an oven. The column can be packed or capillary and is paired with an inert detector that records signals as substances exit the column. Common detectors include flame ionization detectors (FID), thermal conductivity detectors (TCD), and mass spectrometric detectors (MS).

Retention time, the time needed for a component to reach the detector, serves as a basis for identification when compared with standards or known libraries. Quantification is achieved by calibration with reference standards. Modern systems may couple GC to mass spectrometry (GC-MS) for compound identification and structural information, or to tandem MS for greater specificity.

Applications include environmental analysis of volatile organic compounds, petrochemical and natural product analysis, flavor and fragrance profiling, and quality control in pharmaceuticals and foods. GC is especially suited for thermally stable and volatile compounds but is limited by the need for volatile samples and the potential for thermal degradation of sensitive analytes.

The technique was developed in the 1940s by Martin and Synge, whose work laid the foundations for modern gas chromatography. It remains a core analytical method in chemistry and analytical laboratories, often combined with spectrometric detection to provide both separation and identification.