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GC questions
Posted: Mon Feb 07, 2011 10:20 pm
by srikanthearpina
How can we determine the flow rate of the carrier gas and sample? In my case I have to determine hydrogen gas conc. in a gas sample which contains unknown conc. of hydrogen.
detector
Posted: Mon Feb 07, 2011 10:21 pm
by srikanthearpina
What is the best detector for Hydrogen gas conc. determination?
Thanks
carrier gas
Posted: Mon Feb 07, 2011 10:22 pm
by srikanthearpina
Whats d best carrier gas for Hydrogen gas conc. determination. I have options like Argon, Helium and Nitrogen. Which one suits best? I have read that Nitrogen is the best carrier gas. Does it apply to detect hydrogen gas determination?
Thanks
column and detector working theory
Posted: Mon Feb 07, 2011 10:25 pm
by srikanthearpina
What happens to the sample after it gets separated in the column? How does the detector sense the sample (or) the actual connection between the column and detector?
Plz respond soon.
Thanks
Re: GC questions
Posted: Mon Feb 07, 2011 11:13 pm
by tom jupille
I would recommend that you get hold of a good book on basic GC. McNair's book would be a good choice. Here is a link to it on Amazon:
http://tinyurl.com/4mx8rml
Re: GC questions
Posted: Tue Feb 08, 2011 1:12 am
by chromatographer1
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