In reply to Jim Cahill:
Some comments before we address why hydrogen is used . There are several carrier gases used in chromatography Hydrogen , Helium, Argon , Nitrogen . The reason that you see hydrogen often mentioned is based on the detection method. One detector used in the GC is the thermal conductivity detector (TCD) . This detector is base on comparison of the process gas being measured to a reference gas . Hydrogen has the highest thermal conductivity factor of all these gases , therefore hydrogen used as the carrier gas gives you best sensitivity. However if you want to measure Hydrogen you would use another carrier i.e. Nitrogen , again difference in thermal conductivity . Helium is use predominately in the USA , safer, no explosive issues. More if required