Is ammonium bicarbonate volatile ?

[PHOBIUS]

Hi,

The subject of this topic is my main question at the same time.

According to the literature, ammonium bicarbonate sublimates at temperature of 106°C. At the same time, it gets decomposed to water, CO2 and ammonia.

Does it mean, that if I elevate the source block temperature to 130°C (instead of commonly used 100°C), it will result in higher volatility of this buffer ?

Has anyone experience using hydrogencarbonate buffer in LC/MS ?

THANKS.

[Uwe Neue]

We have used ammonium bicarbonate extensively in MS applications, and never worried about it. Please note that according to the Merck Index, ammonium bicarbonate is "volatile with decomposition at about 60 degrees C", not 106 degrees.

[PHOBIUS]

Thank you very much Uwe.

[Bruce Hamilton]

Just to be picky...

The Merck Index also notes that the Melting point is 107.5C ( very rapid heating ) - which I believe would usually determined in a closed capillary tube of suitable pressure rating.

Yes, it is volatile with decomposition at 60C, but users should ensure enough energy is provided to ensure ammonium bicarbonate is fully volatilised, - which should not be problem for the quantities into a MS.

Please keep having fun,

Bruce Hamilton

[Kostas Petritis]

I have tested in the past the volatility of several acids, bases and their corresponding salts at different concentrations by using an evaporative light scattering detector and as you can see ammonium bicarbonate is volatile. The corresponding article can be found at:

chromatographyonline.findpharma.com/lcgc/data/articlestandard//lcgceurope/062002/9090/article.pdf



The online pdf version quality is kind of poor, I can provide you with a high quality one through e-mail if you want...

[Bryan Evans]

For reasons already stated (readily decomposes) - aqueous ammonium hydrogen carbonate solutions
should be prepared daily (24 hr expiration date).

[PHOBIUS]

thanks Bryan,
that is an useful piece of information.

[Uwe Neue]

At pH 10, you do not need to worry about the stability of ammonium bicarbonate. Only when you are trying to adjust the pH to neutral conditions to get to the first pKa of the carbonic acid, this does not work.