Chromatography Forum

Hello

In our lab, we have seen it happen a few times when diethylamine is used as an additive in the mobile phases, that the mobile phase will undergo a color change over time.

Can anyone shed any light on this? Can anyone explain exactly what is the reaction that's causing this?

We are trying to understand the mechanism, so that we can perhaps avoid using DEA in combination with things it doesn't "get along with".

Much Thanks in Advance

Hi Adam

What is the colour change?

What is the mobile phase in which this occurs?

If a mixed phase, have you tried the diethylamine with each component separately to see which one is giving the colour change?

Regards

Ralph

Thanks GOM

We have seen this on two occasions.

- In the first case it was 1% DEA in acetonitrile, with a small concentration of naphthol as internal standard.

- In the second case it was 1% DEA in 90/10 acetonitrile/ethyl acetate

I tend to think it was not reacting with these ingredients so much as with a trace impurity......or itself.......of oxygen.

Any thoughts, or any other experiences that folks may want to share, would be appreciated.

Thanks!!

Oh, and in response to your other question, the color changed from clear to yellow.

The DEA is reacting with the Ethyl Acetate to give you an amide.

Thank you for that reply, but how do you account for the color change in the other solution (just acetonitrile and a low concentration of naphthol). Do you think it might have reacted with the naphthol?

Am I the only one who has ever noticed this kind of color change with Diethylamine?

Hello

Check if glasware (bottles) is really clean, especialy if you're using washing machine - perhaps there are traces of some detergents or cleaning agents.

Regards

Tomasz Kubowicz

DEA will get a yellow tint on its own given enough time.

At my last workplace we had bottles from the 70's and 80's which had turned different degrees of yellow.