Chromatography Forum

We are currently purifying cysteine-MPA (mercapto propionic acid) on C18 preparative reverse phase (Daisogel ODS). We use as mobile phase A : H2O and mobile phase B: TFA 0.1% (No organic solvent). The product was loaded onto the column in a TFA 5% solution. No problems, this process works perfectly but I don't understand why a TFA gradient causes this molecule to elute. If someone know the chemical reason for that...
Thanks
Paul

Sounds to me like your thought process is right. You are already loading the compound in a much higher concentration of TFA, if 0.1% TFA were really the strong solvent. Is this a published method? How well-retained is cysteine-MPA on this column?