Chromatography Forum

Hey,
I was given some advice on this forum a while ago to use a perfluorinated carboxylic acid ion-pairing agent (TFA, HFBA) to alter selectivity for an hplc method. Just wondering how do i do this?...whats the theory behind it?

If your analytes are cationic, the use of anionic ion-pairing reagents will increase the retention of your analytes. One of the mechanism you can think of is that the hydrophobic part of the ion-pairing reagent will interact with the stationary phase and be adsorbed creating a dynamic ion-exchange layer (the polar part will face the mobile phase) which can now further increase the retention of your cationic analytes