LC question

[wrighty]

Afternoon all,

i dont know if i've got this in the right section so apologies if i havent.

at my place of work we tend to degas our LC mobile phases with He. i was asked today why we do this when the Agilent 1100 series systems that we have have got a degasser installed already.

my theory to this is that the He removes the majority of gasses from the mobile phase and the system degasser just ensures that there is no gas left in the phase. does this sound plausible?

i would be interested to hear what other people think.

cheers

steve

[zokitano]

Steve,

You're right about the He usage. Helium dissolves the solvent gases and removes them out of the solvent. I use Agilent 1100 Series HPLC system also, but I never treat my solvents with helium prior analyses, because degassing function properly is done by the degasser unit and it is reliable. I haven't had any problems with bubbles in the system so far.

When I turn on the Agilent system, firstly (after column replacement/installation), I purge the system (out of column flow) with the solvents I'll use. When there are big bubbles in the tubings that lead to deggaser, I turn off the degasser and push them out of the system with high flow (out of column), then I switch the degasser on (when I don't see any bubble in the tubings from the solvent reservoirs to degasser and from degasser to the pump).

Best regards

[DR]

I tend to He sparge my mobile phases despite having degassers. I look at the degassers as a way to keep them gas free as He sparging is only good for a few hours. I don't consider them to be efficient enough to degas a fresh MeOH/Water mixture if I'm uisng a fairly high flow rate. I may be underestimating them, but I've had many more failures with degassers than with any other LC component.