enalapril maleate

[Holly]

I'm testing the USP method for dissolution of 5 mg enalapril maleate tablets but media being 6.8buffer gives me broad peak shape and a small signal on chromatogram. Has anyone faced the same problem? How do I overcome this? I've tried to use a cyano column, but there is interference on chromatogram and k' is < 1,5.

Thanks in advance,

[Uwe Neue]

Enalapril is subject to a secondary equilibrium, where two conformers of the compound interconvert. These two conformers can be separated by LC, which is the reason why you get such broad peaks.

This can be manipulated by changing the pH or by changing the temperature. It is not a column problem, and I would not go for the CN column.

You can get more information on this by looking it up in my book on HPLC Columns on page 362ff in the troubleshooting section.

I can also give you other information, if you contact me.