Has anyone out there had any problems with a Gilson 322 HPLC pump. Mine is three weeks old and I have had the mixing module replaced three times already, and it has now gone again. There seems to be a pressure build-up causing the seals in the mixer to go, but the manometer registers 0.0psi the whole time. The column is not blocked, but the eluent (10%EtOH in hexane)does not pass through the column. I would be grateful if some could shed some light on this problem.

Check with Gilson to find out if they recommend different seals for normal-phase (organic) and reversed-phase (aqueous) operation. Gilson should be eager to help since the system is presumably still under warranty.

further to my last message:

The pump unit has been replaced and after a week of problem free usage, the unit has failed again. The problem seems to be that the pressure transducer. Both on the pump diplay and in UniPoint, the pressure reads 0.0psi regardless of the pressure in the system. This in the past has allowed the pressure to build up until the mixer module ruptures.

The problem seems to occur only when the system has been shut dowm over a weekend.

does anyone have any ideas as to what could be causing this problem?

The problem is being caused by the hexane.Some portion of your system is not compatible with it.
Make sure Gilson knows what your pumping.Does the manual have any info on materials used in the pump or compatability tables?

Cheers Bill,

My supplier assures me that there are no problems with using hexane. I have since found what I believe to be the source of the problem. Operating the pump without the involvement of unipoint gave me a pressure reading. When unipoint is started having started the solvent flowing this way, the pressure is detected.

There is obviously a problen with the computer side of things. My supplier is arranging to replace the PC, and hopefully this will resolve the situation.