By H Michele on Tuesday, August 3, 1999 - 06:50 pm:
I am running a gradient system using a simple 0.1% TFA gradient in which the gradient shows a wavering baseline from 20 - 35% B, but is okay above that. The pumps are Thermoseparations 3200 and are fantastic, but I have this problem lately. I have changed the check valves (inlet and outlet)on pump A (assuming the problem is here when the gradient is more A than B), but the problem persists. I know the fix is simple, but I am just missing something here. Any ideas?
By Mike on Thursday, August 5, 1999 - 05:20 am:
I have seen this at the same gradient composition. I attirbuted it to air in the detector (after changing the check valves) and after purging the flow cell with isopropanol, stopped the problem. You might try this. Remember to purge from the outlet side of the detector to the inlet side. I hope this solves the problem.
By bill on Friday, August 6, 1999 - 04:18 am:
Assuming you are working at a low wavelength (215nm),try running the gradient at 280nm.If your problem is wavelength dependent,consider:1- the mixer 2-degassing 3-flow variations from pump seals etc.
By hmichele on Friday, August 13, 1999 - 06:50 pm:
bill and mike:
thanks for your suggestions. The problems with the pump were multiple and many and your suggestions really helped, but:
it sure didn't help that I found a miniscule piece of sapphire plunger in the liquid end.
Duh. :)
Thanks again.
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