pressure loss and retention loss

[jiangds06]

it is wired that I saw pressure and retention loss in prep scale separation. sample is dissolved in dmso at 1gram/ml, very viscous liquid. It might also have some other organic solvents, such as dioxane, ethyl acetate and hexane. After first several injection, retention was lost and pressure drop from 1700psi to 1600psi. After 100% organic solvents wash, retention and pressure restored.
I never see this before and I suspected that it is because of organic solvents. what do you think?

[uzman]

Assuming you are using bare silica column and normal phase separation , dioxane and ethyl acetate may change your retention times .

[jiangds06]

unfortunately, I am using reverse phase column.

Assuming you are using bare silica column and normal phase separation , dioxane and ethyl acetate may change your retention times .

[yazmer]

what is your mobile phase composition and at what flow rate?

[jiangds06]

I checked the system and might be hardware issue.

what is your mobile phase composition and at what flow rate?

[danko]

There has been an air pocket in the pump head.
the 100% organic treatment has removed it.

Best Regards

[jiangds06]

Yes, you might be right!!!

There has been an air pocket in the pump head.
the 100% organic treatment has removed it.

Best Regards