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Helium - Hydrogen separation
Posted: Thu Feb 09, 2006 12:05 pm
by christiancarioca
I am analyzing a mixture containing He, H2 and CH4, using TCD with Ar carrier. Column 13X does not seem to resolve well between He and H2. Any suggestion to switch to another column? Thanx. Christian
Helium Hydrogen
Posted: Thu Feb 09, 2006 1:23 pm
by chromatographer1
Two choices
First, if short analysis time is a requirement, then choose Molecular Sieve 5A (shorter time for methane elution).
This column requires regeneration from water blocking the pores.
Otherwise the other choice would be Carboxen 1000. This synthetic sieve is not affected by water which it elutes very late (flat baseline).
Call Supelco Technical Service for assistance.
800-359-3041
Techservice@sial.com
I've tried with MS 5A...
Posted: Fri Feb 10, 2006 5:45 pm
by christiancarioca
... but the separation is not as well resolved as I would like. Helium comes first and there is a slight overlap with H2 yet. Any other suggestion?
other columns?
Posted: Fri Feb 10, 2006 7:10 pm
by chromatographer1
You have tried the other columns?
If not, and you must use what you have, then
lower the temperature of your oven,
make a smaller volume injection,
remove dead space from the injection system ahead of the column, and from behind the column before the detector if possible,
OR
connect two 13X columns together.
good luck,
Rod
Good suggestions
Posted: Sat Feb 11, 2006 12:10 pm
by christiancarioca
I used ShinCarbon ST 100/200 mesh, 2m x 1 mm, with N2 carrier, and the separation enhanced significantly. I also reduce the sample loop to less than half of the size I had been using before (I cannot further reduce it because I would be able to surround the sampling valve). I cannot lower the temperature below 40°C (this is Brazil!).
Thank you very much.