I am jumping to a conclusion but from YOUR words, you wanted the flow rate of your sample and of hydrogen. So I assume you are measuring the output of a mixer, mixing a gas sample and hydrogen together and you want to know their concentration in the mixed sample.
Nitrogen is the better choice to measure hydrogen compared to argon or helium.
The thermal conductivity detector measures the changes in cooling rate of a hot wire as different gases pass over it. The gas with the greatest difference in conductivity to hydrogen is the better choice.
You will have a near linear response over two or three orders of magnitude if you use a detector of good design, the proper sample size, and the proper flow rate. These have to be experimentally determined, not quoted as a melting point or density value.
The sample that is injected onto a column is hopefully separated into its components on the column and hopefully all component gases will elute off the column given enough time. Some gases like water may not elute and may stay trapped on the column.
A little study as Tom suggested is a great idea. Perhaps looking at Gow-Mac's web site and other resources on the web might also prove useful.
I am certain you can perform a web search on the topics you seek answers, so I won't do your work for you on that level.
Good luck in chromatography,
Rod
