Hello everybody,
Can someone help me, please.I am working for the first time on capillary anion exchange column and I got in trouble.The column pressure is extremely high-more then 250 bar with 1µl/min flow. I dont know how to regenerate this kind of columns, because I think the column is dead

What type of anion exchange phase are you using? Is it silica based? Is the high-pressure coming from your sample? If so, then you need to use conditions suitable for solublizing the relevant components in your sample responsible for the high pressure. Of course, you'll have to stay well clear of regeneration solutions with elevated pH. However, if you are dealing with a polymeric phase then a good regeneration solution would be one which is extreme in pH and renders the contaminating components non-ionic. Generally, this means you need fairly low pH. With a polymeric anion exchange material I would start with a mixture containing 0.1 molar acid and 50% acetonitrile. If the high pressure is "system related" you would probably be better off backflushing the column.

Thanks Chris,
I am working on silica based column and the high pressure comes from the column.I did the backflush and regeneration procedure- flushing with low pH solution, then with high pH and water and MeOH, but it did not help me. I think there is blockage from a heavy metal salts, because my HPLC system is stainless steel one. What kind of acid do you recommend me to use for flushing.

Elisa,

If you've run high pH solutions over a silica based anion exchange column, there's a good chance you have damaged the bed irreversibly. A point that's generally not understood with ion exchanger materials is that the stationary phase pH can be vastly different from the mobile phase pH. For example, 1 mM sodium hydroxide will make the mobile phase pH 11 but the stationary phase pH could be well over 13 if no other electrolytes are present because the anion exchange sites are highly concentrated on the surface of the support. Then, once the high pH stationary phase is left in this condition it will rapidly undergo self-hydrolysis. So, it's generally not a great idea to use any solution pH which is greater than 7 on an anion exchange material based on silica for any extended period of time. And certain buffers such as phosphate buffers can greatly exacerbate the problem.

But, assuming you're alkaline rinse did not damage the column I would recommend that you rinse it with an acid solution that is noncorrosive such as methanesulfonic acid. If you have reason to believe that the problem is really due to heavy metal salts, I would try treating the column with EDTA at around pH 5-6, first.

Dear sir,
I deal with reverse phase silica based preparative column(for protein purification).But oflate i am having the following problems:
1.high back pressure from column(even with new column frits).
2.Unassumingly low yeilds even after regenaration with 70%MeCN and salt
3.HETP doesnt improve even after repacking ideally.
Could u please suggest effective regeneration procedure and ways to remove colour from the column if any(my load on the column is slightly browinish)