Page 1 of 1
gas generators
Posted: Thu Oct 02, 2008 11:51 am
by mojo
Hi,
We are setting up a new lab and intend to install gas generators instead of piping in the gases from cylinders as we does now. We use nitrogen, helium and hydrogen. I have sourced the helium and nitrogen generators but not a helium genrator. Is there such a thing as a helium gas genrator?
Posted: Thu Oct 02, 2008 12:51 pm
by Consumer Products Guy
No. Some use hydrogen as carrier gas instead of helium, due to helium costs rising and fiite, limited supply.
Posted: Thu Oct 02, 2008 1:17 pm
by DR
^ not to mention that H has better looking Van Deemter plots than He.
( image stolen from
www.chem.agilent.com/cag/cabu/carriergas.htm )
Posted: Thu Oct 02, 2008 5:31 pm
by sassman
Just make darn sure you don't have a leak
Posted: Fri Oct 17, 2008 9:27 am
by CE Instruments
Using a Hydrogen generator you have in most cases not got the ability to make gas fast enough to get the concentration high enough to explode
Buy small generators per GC not one big one. Alternatively (or as well) buy one of Brechbuhlers Hydrogen detectors just to be safe
H2
Posted: Fri Oct 17, 2008 9:59 am
by WK
Hi,
Am I right that if you use 50ml/min FID H2 and 1ml/min column flow and 100ml/min split for 2 minutes at run start - you still need the one with a rating of at least 151ml/min?
WK
Posted: Fri Oct 17, 2008 12:39 pm
by Don_Hilton
At what pressure? At a given current the generator will give a specific number of moles of gas. PV=NRT. (I used to enjoy chromatography until someone pointed out that chromatography is nothing but P chem in a tube!
)
Posted: Fri Oct 17, 2008 2:02 pm
by WK
Hi Don,
Thanks for the reply - I suppose that would depend on the GC manufacturer inlet pressure requirements - my GC requires 60-90psi for hydrogen (both FID and for carrier).
WK
Posted: Tue Oct 21, 2008 11:09 am
by Peter Apps
HI WK
Gas generators need to be generously over specified - work out your actual requirements and double them at least. Then you have spare capacity for different methods, leaky septa etc, and for when the generator starts to show its age. For nitrogen and air generators especially there is a steep inverse relationship between gas flow and gas purity.
Peter