Chromatography Forum

My question is what kind of buffer solution will be efficient for seperating bile acids, such as ursodeoxycholic acid, chenodeoxycholic acid, lithocholic acid, cholic acid, deoxycholic acid..., using UV-detector with C18 Column ? I've already tried with phosphate and acetonitrile by gradient method. Am I doing right? Becasuse I found that they have very poor sensitivity at 210nm UV detector.
Any expert's help would be really appriciated. Especillay, detail condition...
Thanks.

I don't have any experience with these acids but 0.05% phosphoric acid and acetonitrile, detection at 205 nm, works well for many aliphatic acids. In a reversed pahse separation the composition of the buffer is unimportant. The buffer just needs to get the pH low enough to supress dissociation of the acids.