Chromatography Forum

Hello,

I'm trying for a while to perform efficient HPLC separation of monoethanolamine and its degradation products (organic acids, other ethanolamines, ...).
I'm currently using a Hilic mode with 90:10 Acetonitrile:Buffer, in which Buffer consists of a 5mM Ammonium acetate solution at pH 3,8 (obtained by the addition of some acetic acid).
Detection is performed with RID (refractive index detector) and UV-Vis detector at 195nm.

I've tried various eluant compositions as well as various pH values, and I don't obtain nice peaks, separation is most of the time very middle. Does anybody has experience with this kind of analytes?

I also used to work before with a strong cationic-exchange column (Benzosulfonic acid, MN Nucleosil SA). Eluant was 0,05M KH2PO4 at pH 2,6 (obtained with phosphoric acid). The problem was an very important tailing, a rather bad separation. Moreover, two peaks always appeared when analysing pure monoethanolamine. I still haven't identified the first peak (perhaps ionized monoethanolamine)? It was not water, neither eluant peak. Both peak areas were proportionnal to the ethanolamine concentration in water. Has anybody an idea about what it could be?

Thanks in advance for your help!
Grégoire.

I've had good luck using a Dionex CS17 with MSA eluent for amines. It has pretty good selectivity.

Look at this article, it probably describes something similar:

Screening of nitrogen mustards and their degradation products in water and decontamination solution by liquid chromatography–mass spectrometry. Hoe-Chee Chua, Hoi-Sim Lee, Mui-Tiang Sng. Journal of Chromatography A , Volume 1102, Issues 1-2, 13 January 2006, Pages 214-223

With only 10% of a 5mM buffer the overall buffer strength is only 0.5mM. My guess is that you have electrostatic interactions causing the bad peak shapes in your HILIC chromatograms.
With UV at 195 nm you can not really put in any more ammonium acetate so I would go for an alternative buffer salt (Andy Alpert suggested some in a previous post) at a higher concentration.
If you are using a Luna HILIC column you could try to switch to a different column and increase the water content in the eluent (you may even be able to use phosphate buffer if you go above 20% water).

This is an example on GHB using between 20 and 30% buffer in the eluent.

http://www.sequant.com/files/documents/ ... c_Acid.pdf