Chromatography Forum

The new Waters system use the Waters 1525 binary pump with on-line degasser.
A channel: methanol; B: 0.0025M phosphate buffer
Gradient elution: 0min 40%A—20min 60%A
I filtered all the mobile phase and the samples.
But it is easily to block all the parts after the pump. I had change 2 mixturer, several pipes.
It is only two weeks had to ask the technician to come here for repairing.

Today I found that the methanol drown from the head of A pump contain many crystals. I think that the crystals are the phosphate salt, that means the phosphate buffer mix with the methanol before the pump A.

Does somebody has the same problem? How to solve the problem!
Thanks!

2.5 mM phosphate should be quite soluble in approx 50% MeOH.

Have you checked to confirm that your technician is preparing the buffer correctly?

2.5 mM phosphate should be quite soluble in approx 50% MeOH.

Have you checked to confirm that your technician is preparing the buffer correctly?

Thanks!


the mobile phase is made by myself.

I had test the solubility of the mobil phase 40%methanol+60%buffer and 60%methnaol+40% buffer, all mobile phases are good.

the question is " why the cystal can come at the A pump head", as I think here is the pure metanol.

I would not be surprised if at some point in time somebody confused the A- and the B-line, resulting in buffer in the methanol line.

Solution: rinse both the A and the B line with water, then go back to the normal operation.

Is this the only solvent system you are using?. If so, then Uwe has identified the problem and solution.

If you are using the system of a range of different solvents, then it is quite likely that your procedures for system flushing before changing mobile phases is not going to, or remaining at, high water content in channel A long enough to remove all the buffer.

If your column doesn't like 100% water, then 90% water is usually enough to remove residual buffer from all of the system, not just the mobile phase channel lines. If you have an almost blocked line, then slightly warming the mobile phase in the reservoir may help redissolve precipitated buffer.

Please keep having fun,

Bruce Hamilton