You should use nitrogen carrier gas if you want linearity of response over a wide range.
Do not use Helium unless your measurement is starting at about 10% and above. The measurement will not be linear at the low end or accurate below 10% unless it is below about 4% to 0%.
You can use a packed Carboxen 1000, or Carboxen 1010 capillary, or packed or capillary molecular sieve columns, 5A or 13X.
Any questions, feel free to contact me directly.
Rodney George
Senior Research and Development Scientist
Gas Separations Research
Supelco
595 North Harrison Road
Bellefonte, PA 16823
814-359-5737 voice
814-359-5459 fax
rgeorge@sial.com