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Gas bubbles at 40min
Posted: Fri Jan 13, 2012 7:39 pm
by acetone
Hi,
My system seeing the gas bubbles at 40min of 60 min gradient elution.
Flow rate: 0.5 ml/min
A: NaOAc buffer Ph6 B; MeOH
Shimadzu 10AVP system
Degass by He, always see bubbles at 40min no matter how long the mobile phases degassed.
Please supply some hints.
Regards,
Acetone
Re: Gas bubbles at 40min
Posted: Sat Jan 14, 2012 3:06 am
by tom jupille
First of all, are you sure they really *are* bubbles (as opposed to junk eluting from the column)?
Assuming they are bubbles:
Make sure that you degas continuously (not just "one shot"), because once you stop the He, your solvents begin to re-equilibrate with the atmosphere.
Keep the runs of teflon tubing between the reservoirs and the pump(s) as short as possible. Teflon is somewhat permeable to air (that's why I like the in-line membrane degassers that sit immediately upstream of the pump!).
Re: Gas bubbles at 40min
Posted: Fri Jan 20, 2012 5:26 am
by ZeroAir
Yes, buy a degasser to sit on top the pump. Problem solved.
Re: Gas bubbles at 40min
Posted: Mon Jan 23, 2012 11:56 am
by Peter Skelton
It's also a good idea to mix your A solvent to the starting mixture of your gradient, and re-adjusting the gradient programme to keep the slope the same.