Chromatography Forum

I have a question that may be very elementary. Since I am new to the Waters 2695, any help will be greatly appreciated.

Every time I do an injection, the system pressure drops by 600-700 psi (from about 1200 psi to 500 psi). This lasts only for a second or two and the pressure will slowly go back up. Is this normal for the Waters 2695? I have rebuilt the seal pack using Waters parts and replaced the syringe but the problem still persists. I think a couple of columns have already been ruined by this pressure fluctuation. Any suggestion as to how I can stop this? Thanks!

Do you see the same pressure drop in both directions (i.e. when the valve goes from "load" to "inject" and then again from "inject" to "load")?

Actually, the pressure goes up (to 2000 psi) first and then drops down to 200-300 psi on injection.

Actually, the pressure goes up (to 2000 psi) first and then drops down to 200-300 psi on injection.

Probably the bypass channel of the valve is partly clogged