Carrier gases (mobile
phase) must be chemically inert He, Ar, N2, CO2 even H2 and mixtures 95/5 N2/CH4
Often detector
dictates choice of carrier gas
In GC sample doesnt
really interact with carrier gas (unlike HPLC), temp
controls partitioning
Often necessary to
purify cylinder gas with a trap, scrubber or cartridge of
molecular sieves (or buy high purity gas) O2 ppm Hc
The move today is
away from gas cylinders toward gas generators (extract pure carrier
gas from air)