Gas Chromatography

Gas Chromatography (GC) is a complimentary technique to other chromatography techniques. It is used to separate, identify and analyse different volatile and semi-volatile organic components of the sample. In GC techniques the sample solution is injected into the GC instrument and vaporised. 

The carrier gas (mobile phase) transports the sample molecules to the column (stationary phase) where the GC column is heated in the column oven using a programmable temperature gradient to enable the elution of the more volatile components first and then the less volatile components later.  

The different components of the sample travel through the stationary phase at different rates and this is how the separation is achieved. The eluting components are detected on the detector and the signal is analysed by the software to produce a chromatogram.

Rubber Consultants use different types of GC detectors, such as:

GC-FID - Flame ionisation detection is the most common detector used in GC analysis. Once the components are separated in the capillary column, they pass through a hydrogen flame which ionises the carbon atoms. 

These ions are detected by a collector electrode and the current generated by these ions is proportional to the mass of carbon. The FID detector is used for detection and quantification of organic compounds.

GC-MS - Mass spectrometer utilised as the detector. The main advantage of this detector is the ability to identify ‘unknowns’. Mass spectral libraries are commonly used to perform the identification.

Headspace GC-MS – The use of a mass spectrometer detector to analyse the headspace of an incubated sample sealed into a headspace vial. Primarily used to observe and quantify volatile organic components.

GC-NPD - Nitrogen-phosphorus detector is specific to nitrogen and phosphorus containing compounds. The NPD detector is similar in design to the FID, but is uses a thermionic NPD bead to generate ions in a hydrogen and air plasma.

GC-NCD - Nitrogen chemiluminescence detector is a nitrogen specific detector used primarily for the analysis of nitrosamines.