By Yong Men on Tuesday, October 29, 2002 - 06:36 am:
Hello,
I have a problem in hydrogen detection on Agilent 6890GC. I have two clolumns (HP-PLOTQ and HP-MS5A) and one TCD. Helium is used as carrier gas. The sensitivity of hydrogen is very low, compared with other components (CO, CO2, N2, O2). I am considering to change carrier gas into He/H2 or He/Ar gas mixture in order to improve the hydrogen sensitivity while keeping the sensitivity of CO, CO2 etc. Can anybody tell me some further information (pecentage of each gas and so on) about gas mixture as carrier gas? Is there an explosion risk by using He/H2?
Any input will be appreciated.
Yong
By Anonymous on Tuesday, October 29, 2002 - 06:54 am:
I have used 8.5% hydrogen in helium as TCD carrier gas in the past, so that all hydrogen peaks appear as negative peaks, and use use switched polarity to quantitate.
By Yong Men on Tuesday, October 29, 2002 - 12:24 pm:
Thanks for your kind help. One more question is how good the sensitivity is for other components such as CO, CO2 etc after change of the carrier gas. I ask because I have only one analysis channel and one detector. Hope to get further information. Could you recommend a relevant publication?
Thanks again.
Yong
By Anonymous on Wednesday, October 30, 2002 - 07:48 am:
I didn't really notice a sensitivity difference vs. pure helium.
By Kuba on Thursday, October 31, 2002 - 05:53 am:
Hello Yong,
Can you describe % content of your mixture?
By Anonymous on Thursday, October 31, 2002 - 08:15 pm:
You might try argon doped with methane as a carrier since helium and hydrogen have little thermal conductivity differences. Although, it will reduce sensitivity of N2 and O2 the methanizer will improve the loss of sensitivity of CO2 and O2 if sulfur compounds are not present.
By yong men on Tuesday, November 5, 2002 - 02:53 am:
Sorry I reply so late because I was not in my office in last few days. The main compnents I want to analyze consist of 10-50% hydrogen, 15% CO2, 1% CO or lower, 10% methanol, some water and inert gas carrier gas (N2 or Ar). I just want to quantitate H2, CO2, CO and CH3OH. The only problem by using He as carrier gas is the poor sensitivity of hydrogen. The factor to other component is about 100 so that it is difficult to get a quantitative result. I do not want to lose much sensitivity of CO2, CO. I have tried 50% H2 and 50% N2 mixture for analysis. I got a single peak instead of claimed W shaped peak after changing polarity of TCD. Next I will try Ar to see how good it is.
Thank you all for your kind reply.
Yong
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