Shift of retention time and sudden presure drop - help

[asm]

I changed the outlet ball valve, with one of the other system - same problem.

The last possibilities are the Active Inlet Valve or the Pump Seals?

[Peter Apps]

Should the pump be adjusting for the compressibility of the mobile phase components ?, if so, maybe that is malfunctioning. NB that the two pressure traces have different scales so the difference between them is less than appears at first glance.

Peter

[LCbob]

Hi

It looks like the cartridge or the whole active inlet valve is the issue. Do you check the tubing going into the active valve is seated correctly though, you maybe sucking a little air into that side. Doubtful it is the pistons seals. If possible carryout the leak test for a binary...it built into many versions of chemstation of its Gameboy.

[asm]

Today I replaced the Active Inlet Valve Cartridge and it works like it should.

[MikeT]

I had exactly the same problem. By the way did you try premixing the solvents so mobile phase only flows through one line? This might work. Honestly it is probably not bubbles but a dirty flow cell. I had accidentally broke my flow cell when inspecting it. When the flow cell was changed the problem went away. I would check the windows of the flow cell to see if it looks cloudy or dirty. Just be careful if you take it out as it is easy to break.
Now if it is airbubbles run isopropanol, as IPA is miscible with air and can get rid of bubbles.

[H3O]

Hello, chromatographers! I have a problem with pressure on Agilent 1100 (quat pump).
Fluctuations of pressure are extremally high. The active inlet valve is OK, because it's cartridge was changed some months ago. The outlet ball valve looks nice too. Any leaks of eluent were not observed. I don't understand where the pressure leaks.
Did somebody had such problem? Reply this message, if you know how to fix this problem, please.
I attached the screen shot of ChemStation where you can see chromatogramm with abnormal pressure diagram.

[asm]

There is no screenshot.

Which solvents/column do you use?

[HPLCaddict]

The active inlet valve is OK, because it's cartridge was changed some months ago. The outlet ball valve looks nice too.[/img]

"Some months ago"? That can be a long time .
"Looks nice"? Look is one thing, does it WORK nicely?

With pressure fluctuations, check valves are my first suspects. Don't trust them, check them!

[H3O]

There is no screenshot.

Which solvents/column do you use?

Sorry, but I don't know why picture didn't attach.
I used Waters Symmetry C8 (250 mm; 4.6 mm). Solvent A: H2O; Solvent B: CH3CN.
It was carried out a solv. B gradient and I observed the increasing of pressure amplitude with percentage rising of solv. B (CH3CN). I suppose the reason is valve "B" in multi-gradient assembly (G1311-67701). Do you agree with me?


1280x1024(211.54 kB)

[H3O]

"Some months ago"? That can be a long time .
"Looks nice"? Look is one thing, does it WORK nicely?

With pressure fluctuations, check valves are my first suspects. Don't trust them, check them!

Thank you for advice!
I can't attach image due to unknown reason, so look the picture in this link, please:
http://www.fotolink.su/v.php?id=21a18be ... 893df5cc9c
Maybe you have ever seen such problem and could determine the reason more precisely.

[asm]

Hello,

I'll suggest a little test-method. 5min 100% solvent A, 5 min 100% A -> 100% B, 5min 100% solvent B.

Then you should see, which channel is the problem.

[H3O]

Hello,

I'll suggest a little test-method. 5min 100% solvent A, 5 min 100% A -> 100% B, 5min 100% solvent B.

Then you should see, which channel is the problem.

Thanks, I shall try it.