Working principle: The working of this instrument is based upon the principle of chromatography, where a sample is separated into its various components by means of passing it between two phases namely stationary phase and mobile phase. In gas chromatography the mobile phase is inert gas like helium or nitrogen. The sample is vaporised by heating after injecting it into the instrument. The vapors are then carried by the career gas over a column (stationary phase) where various components get separated based on their affinity with the column. The column generally used these days is a capillary column with internal diameter of around 0.1 to 0.5mm and length of around 30 meters. The column is heated over a range of temperature. The separated components are then detected using various detectors, where the most commonly used detector is Flame Ionisation Detector (FID).
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