High backpressure

[zhuwj007]

Hi, everyone,

Please help me on the question below.
Why dose my PA1 column (including guard column) have high backpressure that is about 1200psi when the flow rate is 0.10 ml/min? The cause? And how to avoid it happen again?

My IC module: DX600 of 2mm-system
Mobile phase: 200mM NaOH

Await for your reply and thanks in advance.

zhuwj007

[Chris Pohl]

zhuwj007,

To answer this question we need to know more information. The pressure you list certainly is abnormal but was this high-pressure due to a gradual increase in pressure or a sudden increase in pressure? What eluent are you running through the column? What type of samples have you been injecting? Most of the time pressure problems are connected with particulate in the sample. Often the problem can be result by simply reversing the flow and sending the column effluent to waste but in some cases it's necessary to replace the inlet frit.

[zhuwj007]

Hi, Chris! )

Thank you very much for your response!

I guess my column is blocked by something or with other causes and I can do nothing about it for I know little about the column.

Recently I try to find some technical articles about IC column which is quite different from HPLC column in order to avoid such things happening again. But articles from Dionex.com can not solve my problem.

Would you please give me more suggestions?

p.s. According to Dionex reversing the flow is not recommanded way to clean up columns. Do it harm to columns? How do you carry out it?

[Chris Pohl]

There really isn't a problem with reversing flow on Dionex columns even though you may have heard to the contrary from "Dionex" (considering the fact that I designed this column and I'm employed by Dionex, I guess I'm qualified to tell you this information incorrect). The only thing to be concerned with is the status of the column prior to reversing the flow. A properly packed column in good condition can be reversed with no adverse effects. However, a column with a bit of headspace can suffer a substantial degradation in performance if you reverse the flow (this is regardless of the column type). I suspect that the original recommendation against reversing the flow may have been a manifestation of the relatively poor bed stability of first generation ion chromatography columns. Of course, there are other possible scenarios which will give you a high backpressure including the presence of organic solvent in your mobile phase.

[zhuwj007]

You design the column, cool!

I will have more questions to ask you in the future. You don't mind, Right?

zhuwj007 with best regard

[Chris Pohl]

zhuwj007,

Sure, it's totally okay if you want it e-mail me directly or post additional questions here in the Chromatography Forum the depending upon whether or not you think your questions might be of general interest to other readers.

Chris

[Mat]

Yes, post them here!

I had the luxury of being able to test the reversed flow on a column we already gave up (luxury because I had the time to do so), and while it didn't help much, it didn't hurt either, no resin leaking out...

It was a Dionex AS15 column. After reading the instruction manual, I also believe it has the same size of filters on both ends, if I didn't read something wrong out of it.

But it's always better and easier to know before.