[goldy]

HI all,
I bought normal phase Diol column. During installation I mistakely washed the column with Hexane but the packing column was acetonitrile. Immediately after I washed column with ethylacetate to remove the hexane and started anaysis. For short time it worked but after some time the pressure became unstable.  After that I washed the column with isopropyl alcohol overnight at low flow rate but still has same problem. Please suggest me the way to fix this pressure problem.
Thank you in advance.

[aglasshalfempty]

When you say the pressure becomes unstable, what do you mean?  High pressure, low pressure?  When you say "For short time it worked", how long did it actually perform as expected?

[goldy]

When you say the pressure becomes unstable, what do you mean?  High pressure, low pressure?  When you say "For short time it worked", how long did it actually perform as expected?

Thank you for the reply. The pressure goes down (upto -). when the pressure became stable during solvent run ,I injected the sample and engagged in other work but when I saw the chromatogram it was stopped due to low pressure. Then I again washed with isopropyl alcohol and again equilibrated colum with the desired solvent(Hexane 80% to IPA). Then the same problem persisted.
If you have any idea about fixing this problem then please reply me as soon as possible.
Quick fluctuation in pressure will be the best word to describe this pressure condition.
Thank you very much.

[Golden_4_Life]

At this point, you have rinsed your column with the mobile phase, then followed by an isopropanol rinse and yet the problem persists as a transiently fluctuating drop in column Pressure. To my limited knowledge, this reprsents a problem with permeability of the packing bed material towards the mobile phase while it perfuses in the column bed. Pls try this: 1) reverse the orientation of your column so that the "flow direction arrows" are pointing towards the INjector, then and rinse first with methanol:water. 10 minutes @ 2 mL min-1 should suffice; so that the "flow direction arrows" are pointing towards the Detector, then rinse with 100% methanol for same timeXrate. 2) Re-reverse your column and put in proper orientation, then pump through your mobile phase.  This ought to deactivate the diol residues in the column packing bed and fix the problem?

[goldy]

At this point, you have rinsed your column with the mobile phase, then followed by an isopropanol rinse and yet the problem persists as a transiently fluctuating drop in column Pressure. To my limited knowledge, this reprsents a problem with permeability of the packing bed material towards the mobile phase while it perfuses in the column bed. Pls try this: 1) reverse the orientation of your column so that the "flow direction arrows" are pointing towards the INjector, then and rinse first with methanol:water. 10 minutes @ 2 mL min-1 should suffice; so that the "flow direction arrows" are pointing towards the Detector, then rinse with 100% methanol for same timeXrate. 2) Re-reverse your column and put in proper orientation, then pump through your mobile phase.  This ought to deactivate the diol residues in the column packing bed and fix the problem?

Thank you for the reply. But I don't want to deactivate the diol. As the column contains silica  I think washing with water will deactivate silica but I don't want that. Washing column in reverse direction is a good idea. I will try that.
If you or anybody has more idea about this problem then please help me.
Thank you very much.