By Anonymous on Thursday, January 17, 2002 - 06:37 am:
I work on waters HPLC Alliance systems most of the times using binary and gradient methods. In that I have observed the pump to malfunction (loses priming)when a combination of 0.02M disodiumphosphate buffer as mobile A and 80:20 mixture of acetonitrile and water as mobile B is run .
Further this happens exactly when the gradient rises to 100%B in a span of 15 minutes or less .
Though I am able to understand vaguely as the buffer precipitation in the mixing chambers, I am not able to clearly estimate why it happens,
Have any one observed the same pattern and what should be done to avoid this problem without further occurring.
regards
By Mike Schulz on Thursday, January 17, 2002 - 12:58 pm:
In a prior life I've had lots of problems pumping 100% acn w/ Waters 616 pumps. Waters tech says noone else has this problem, except EVERY pump of ours did this. My understanding is that the check valve cartridges are lousy and easily overtightened, which is why they gave us mini torque wrenches instead of redesigning the valves. Simple loosen and retighten the valve and prime is restored. I do not know if this applies to Alliance, though. We were blamed by Waters tech for every failure of this type.
By Anonymous on Monday, January 21, 2002 - 10:33 am:
Other pumps have problems with 100% ACN besided Waters. Shimadzu does as well. It is check valve related. They get stuck (I can't remember if it was the inlet or outlet).
If you want to avoid this. Simply add 5% - 10% MeOH to the ACN. It'll work then and the slight increase in the polarity of the MP will hardly be noticed.
By Russ on Tuesday, January 22, 2002 - 12:30 am:
We have several Shimadzu systems and have not had problems using 100 % AN in a pump. We also rarely have problems with check valves (lasting over a year without cleaning or replacement). We filter our solvents daily; don't know if that helps or not. One thing we did notice was that if air got in the solvent inlet line, it was easier to get the pump to prime if you manually pulled the air through the pump drain before using the pump purge. If we didn't, some instruments would have difficulty priming.
By Anonymous on Friday, January 25, 2002 - 05:29 am:
The solubility of inorganic buffer substances like phosphates are very low in solvents, especially in acetonitril. This is the reason of precipitation.
By Anonymous on Thursday, February 28, 2002 - 09:58 am:
Hi
Try Agilent HP1100 pumps. I have used it several times and it has no problem
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