How gas chromatography works

Gas Chromatography (GC) is used to separate volatile components of a mixture.  A small amount of the sample to be analyzed is drawn up into a syringe.  The syringe needle is placed into a hot injector port of the gas chromatograph, and the sample is injected.  The injector is set to a temperature higher than the components’ boiling points.  So, components of the mixture evaporate into the gas phase inside the injector.  A carrier gas, such as helium, flows through the injector and pushes the gaseous components of the sample onto the GC column.  It is within the column that separation of the components takes place.  Molecules partition between the carrier gas (the mobile phase) and the high boiling liquid (the stationary phase) within the GC column. After components of the mixture move through the GC column, they reach a detector.  Ideally, components of the mixture will reach the detector at varying times due to differences in the partitioning between mobile and stationary phases.  The detector sends a signal to the chart recorder, which results in a peak on the chart paper.  The area of the peak is proportional to the number of molecules generating the signal.