Chromatography Forum

Hello,
beta keto esters gives very bad peak shape by RP HPLC this is due to the keto-enol tautomerism.I found a article where mixed mode columns (SIELC) has been used for analysis. Are there any other mode by which proper peak shape can be obtained for these compounds.


Santosh

If the problem is really due to tautomerism, try increasing the temperature. The idea is to speed up the interconversion so that the system "sees" essentially one average state. That's a trick that's commonly used to overcome the analogous problem with mutarotation of sugars.

Here is article published by Pfizer scientists. They used Primesep mixed-mode columns. They tried various traditional approaches and got the same problem as you have:

"Beta-diketones: peak shape challenges and the use of mixed-mode high-performance liquid chromatography methodology to obtain fast, high resolution chromatography". by Rance MJ, Wilson S. in Journal of Chromatography A Volume 1217, Issue 12, 19 March 2010, Pages 1912-1915.

Contact me by email if you have questions.

Also, tautomerism is usually strongly influenced by pH, I would think that an acidic mobile phase should speed up the reaction sufficiently.