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GC-FID shifting from He to N2 carrier gas
Posted: Wed Sep 03, 2014 2:06 am
by HeyAj
Good day.
Since He is expensive, I am tasked to change the carrier gas to N2. The GC supplier said that we have to change the molecular sieve also. Is this really necessary? After all, it is just for removing the slight traces from the UPS gas.
Are there other things I need to take note of when changing carrier gases? I am ready to change the chromatographic conditions to maintain good separation.
Thank you.
Re: GC-FID shifting from He to N2 carrier gas
Posted: Wed Sep 03, 2014 6:31 am
by kubowicz.tomasz
Hello
Just find suitable trap for carrier gas (Big Universal Trap, Hydrocarbons) and remember to reconfigure gas type in inlet EPC setting.
Regards
Tomasz Kubowicz
Re: GC-FID shifting from He to N2 carrier gas
Posted: Wed Sep 03, 2014 12:30 pm
by MSCHemist
Nitrogen will typically double the length of time per GC run. Hydrogen on the other hand will reduce it significantly. Agilent as a method translator that is pretty good. Baiscally you need to decrease the linear velocity and temperature ramp and increase hold times.
You may need to adjust the makeup gas flow slightly since the flow rate of nitrogen will be less than helium but it makes very little differce (maybe 0.5 ml/min out of 30).
Re: GC-FID shifting from He to N2 carrier gas
Posted: Thu Sep 04, 2014 8:58 am
by ATAlR
I'm using 3 port selection valve for switching between He or N2 carrier gas, with no hardware adjustment (only column and liner), without problems
Re: GC-FID shifting from He to N2 carrier gas
Posted: Thu Sep 04, 2014 10:02 am
by dblux_
I'm using 3 port selection valve for switching between He or N2 carrier gas, with no hardware adjustment (only column and liner), without problems
If you do not define type of carrier gas for inlet you won't get proper flows through column. EPC needs gas declaration to properly calculate and control gas flow.
Re: GC-FID shifting from He to N2 carrier gas
Posted: Fri Sep 05, 2014 7:16 am
by CE Instruments
No details about the method you are running
Why pick Nitrogen as carrier ?
If you are running a capillary method you should pick Hydrogen as your carrier it will be much easier to transfer methods as you get better separations. If packed then Nitrogen might be a suitable alternative. No GC info. so we don't know if your GC supports either alternative without modification.
Re: GC-FID shifting from He to N2 carrier gas
Posted: Fri Sep 05, 2014 8:56 pm
by AICMM
HeyAj,
ATAIR is correct, you can switch between N2 and He if you only run a few samples per day and it is a 5890. Please feel free to review an application note on this:
http://gcsrus.com/applications.htm (click on What's new.) On the other hand, if you are running a 6890 or a 7890, the EPC will not like an He/N2 switch so H2 is a more appropriate switch. If you are running lots of samples per day, a complete switch to H2 or N2 may be appropriate.
Best regards,
AICMM