Problems with solvent in aa analysis

Chromatography Forum: GC Archives: Problems with solvent in aa analysis
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Wednesday, August 28, 2002 - 09:10 am:

I am trying to perform an aa analysis. I use as a solvent a gradient program with sodium acetate (+Triethylamine+phosphoric acid pH=5.05)/ACN/Water. If I make a run (without injection) I obtain a lot of enormous peaks. It seems something that elutes with the buffer, then remains retained in the column and finally elutes with the organic. Iíve change everything (column, solvents,...) and every time I have obtained the same. What could be the problem?
I would welcome any replies
Best wishes


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Kostas Petritis on Wednesday, August 28, 2002 - 09:58 am:

Could you provide us with some additional information?

aa does it means amino acid analysis?
What is your detector?
What is your column? (C18 I guess)
Have you changed the additives (salts) as well? If this is an impurity problem it might be in the additives and not in your solvents.
Is this the first time that you are trying this method or have you tried it in the past and worked fine?

Kostas


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Kostas Petritis on Wednesday, August 28, 2002 - 11:32 am:

Also...

Is the retention time of these peaks the same from run to run?

What is the shape of these peaks? More like very intensive narrow peaks, or tailling ones?

Kostas


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Mike on Saturday, August 31, 2002 - 04:59 am:

Guess you may need to do a run using other solvent to check if the column is not contaminated. Or there might be other problems. Please provide some more details.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Armando on Friday, September 6, 2002 - 08:47 am:

If your peaks appear only during the gradient probably you have problems with solvents or additives. If solvent or additive quality is not adequate then ghost peaks may appear, mainly if they are organic compounds. Check the organic components, specially triethylamine.
Have you tried gradients from water to acetonitrile without additives? If no peaks appear then you can test the other components by injecting and running gradients.
I have assumed that you are using a reversed-phase column and I made simplifications. You should provide more information, as previously pointed out.


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