unknown peaks in anion exchange

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jithendran's picture
unknown peaks in anion exchange

Hi there,
I had been using tris buffer and sodium phosphate buffers at ph 7.9 on my anion exchange column. I could see few clear peaks in blank runs ie with out any sample injection. I strongly suspect the reagents as we ruled out the chances of involvement of the column or LC system in this problem. Previously I was using reagents sodium phosphate and tris from other brand, I tried your 99.9% trizma. Now the peak area and peak numbers have come down, but still could see clear peaks. Can I ask you if you have come across such a problem asked to you before and if do you have a better grade tris and Nacl (in eluting buffer) with possible little impurities that are not picked up by anion exchangers.


Dr. Analytical
Dr. Analytical's picture
What is in the "blank"

What is in the "blank" solution that you are injecting?  Is it the same as the mobile phase, or is it prepared separately?

At what times do the peaks elute?  Do these times match with any known anions - chloride, sulfate, phosphate, etc?

You should also check the quality of your water. 

Evilyn's picture
Are running a gradient

Are running a gradient starting with NaP04 (A) and using Tris to elute?  Why not use NaCl to elute?

Try running 100% A and 100% B and look at the chromatography with A and B blanks respectively. 

I'm w Dr. A--we need more info to help you.

jithendran's picture
Hi Dr. analytical and Evilyn,

Hi Dr. analytical and Evilyn,

Sorry for delayed reply, I have stopped working on the project (as you can understand priorities change in a industria setup).

Any way,

Answer for you Que are,

Blank is without any injection at all.

I would think all these anions you mentiones while elute out in void vol of the column.

I m using salt gradient onlt (NaCl)
thanks for you help.