Pb of CLHP with both chlorhexidine and lignoca

[Lukasso]

Hello everybody,
I have a problem with the separation and the dosage of chlorhexidine digluconate and Lignocaïne chlohydrate both in solution together, i have peaks tailing, especially with the chlorhexidine. I am using a C18 column and a mobile phase containing water/methanol.
Float rate= 1,5 ml/min
If someone could help me, it would be so great, thanks a lot.
A student...

[CSV]

Have you tried exchanging the waterportion of the mobile phase to an acidic buffer? (Phosphate buffer etc) Maybe, your amines are tailing due to unspecific adsorption to the silica?!!

[tom jupille]

I'll second CSV's suggestion. It's a good idea to use buffers any time you are running ionizable compounds.