Varian CP-3800 GC-FID:
Gas Chromatography
What is GC?
Gas Chromatography, or GC, is a separation of compounds in the gas phase based on the same types of interactions as in HPLC. Only volatile organic compounds can be used. Compounds are separated due to differences in their ability to partition, or transfer between the stationary and mobile phase. Usually this partition is based on polarity when doing GC analysis. The analysis is done at high temperature, usually 5-10oC higher than the highest boiling point in the mixture.
What does FID mean?
FID stands for Flame Ionization Detector. What that means is that as the effluent (carrier gas and any organic compounds) comes out of the column they are ignited in a flame made of hydrogen and air. The compounds produce ions as they burn. These ions conduct electricity. Changes in current within the flame are measured and sent to the computer to be seen as peaks on the chromatogram.
FID is a good general detector for organic compounds, and is able to detect at the nanogram level.
(Picture from http://www.shu.ac.uk/schools/sci/chem/tutorials/chrom/gaschrm.htm)
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