pressure drop during the run

[xiuminchen]

Hi,
I have a problem of our Agilent 1200 HPLC. The pressure is stable when I don't inject the sample, but after injection (around 5-6min) the pressure suddenly drops to almost 0 and increases again soon. Does any one know why is that?
thanks
xiumin

[KM-USA]

Post your gradient conditions.

If isocratic, you've really got issues !!!

[xiuminchen]

It is isocratic. And there is a leak from the bottom of active inlet valve. I changed pump seal and inlet valve cartridge.It still leaks.

[xiuminchen]

Should I change the Active Inlet Valve too?

[Consumer Products Guy]

It is isocratic. And there is a leak from the bottom of active inlet valve. I changed pump seal and inlet valve cartridge.It still leaks.

Yes, active inlet valves can leak over time; you state "leak from the bottom of active inlet valve".

Also, sometimes the two pistons in the pump head get scratched and need replacing. I'll assume that you actually changed both piston seals. Also, the outlet valve can leak and trickle down. And did you use a new gold seal when doing that active inlet valve cartridge?

If your leak is truly "from the bottom of active inlet valve", replace that. It "ain't gonna" heal iself.

[xiuminchen]

thank you very much. I will change the active inlet valve. When you say gold seal, do you mean the gold seal in the purge valve or in the outlet ball valve? I change the purge valve gold seal but haven't change the outlet ball valve gold seal.

[xiuminchen]

Can anyone tell me why the pressure drop only happens when I inject the sample? I just did the leak test, every thing is fine.

[uzman]

Check and replace rotor seal.

[xiuminchen]

we just changed rotor seal and I ran the sample on the following day, the leak came out from active inlet valve again. So, I will change active inlet valve and see whether it will solve the problem.

[xiuminchen]

Hi, the problem solved after I change active inlet valve.