Gaschromatography (GC and GC-MS)
Gas liquid chromatography (GLC) or simply gas chromatography (GC) belongs to partition chromatography which is widely used as an analytical method for separation of mixtures in individual chemical compounds. GC can only be applied for substances which are gaseous or volatile at elevated temperatures. A gaseous medium (mobile phase) is applied for the separation of the sample components during their transport through a column. Inert gases like nitrogen, helium or hydrogen are used as carrier gases. Today the open tubular GC is commonly applied. The capillary columns are made of fused silica with an inner diameter of about 30 - 500 µm coated with polyimide. The inner surface is covered with a thin film of polyorganosiloxanes (stationary phase). By variation of the functional groups of polysiloxane the polarity of the stationary phase can be changed in a wide range allowing the analysis of unpolar and polar compounds by GC.
Special features of GC
In gas chromatography compounds are separated according to their boiling points and/or polarities and in case of special stationary phases due to specific interactions (e.g. in chiral GC). After separation the compounds are commonly detected by their combustion in the FID or with a mass selective detector (MS). Moreover a number of selective detectors are available. The gas chromatograms can be quantitatively evaluated by internal or external calibration. The obtained mass spectra in MS can be used for identification of unknown compounds.
Following GC systems are available:
- GC-MS/ FID (Gaschromatograph coupled to mass spectrometry (MS), Agilent 5973N, with Gerstel thermodesorption and cooled injection system, electron impact ionization)
- Thermodesorption/pyrolysis-GC-MS, (Fa. Fisons with GC2-chromatography)
- Aromatic hydrocarbons
Volatile halogenated hydrocarbons