gas generators

[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?

[Consumer Products Guy]

No. Some use hydrogen as carrier gas instead of helium, due to helium costs rising and fiite, limited supply.

[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 )

[sassman]

Just make darn sure you don't have a leak

[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

[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

[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! )

[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

[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