HP 1100 - Drifting baseline problem!!

[hluong68]

Hi all,
I am in some desparate need of advice. I have a HP 1100 that is running on a Jordi GPC column with chloroform as eluent. while pumping at about 1 ml/min I am seeing pressures between 230 - 270 bars. Anyone know what's causing this - better yet, anyone know how to get rid of this?
The seals on the pump were recently replaced if that helps.

Thanks very much!

[Consumer Products Guy]

Do you mean the pressure fluctuates? Are you using an isocratic pump, bypassing the multi-channel mixing valve with the threaded adapter, or just setting all the unused channels to zero? In other words, supply more information. One way to see if it's column related is to substitute a different column (you may first need to run some intermediate solvents through that before you use chloroform).

[Bruce Hamilton]

Assuming that you haven't changed samples, methods, or the hardware ( such as adding PEEK lines ), then the obvious actions are:-
1. Disconnect detector, should be no change, if pressure drops, detector is blocked - very unlikely.
2. Replace column with a connector. Does the pressure drop to near zero?, If so, column inlet frit, or column, is blocked. Replace or clean.
3. Bypass injector, put restrictor ( or column ) directly onto pump outlet line. If pressure drops to near zero, injector is blocked.
4. If pressure is still high, then pump outlet line/filter/mixing valve is blocked. Clean/replace.

Given that pump seals have been replaced ( presumably with chloroform-rated material ), the most likely cause is particles of dirt or gunk blocking one of the capillary lines, mixing valves, or filters. Ensure that the system was flushed with a chloroform-miscible solvent, including filling sample loop.

You may be able to backflush blocked lines, but more complex assemblies will require service kits. Don't backflush the column unless Jordi says that's OK.

Please keep having fun,

Bruce Hamilton

[ljc]

The little white filter insert inside the purge valve might be plugged up with seal wear material if you are seeing high pressure with the column removed and/or the valve opened up. Remove the purge valve with the flat wrench, the filter is beneath the gold seal. Also, I think that Agilent has special seals for NP solvents like CHCl3 that might be necessary for your application.