Primesep® mixed-mode stationary phases provide multiple types of interactions with analytes. Ionizable compounds interact with the stationary phase by reverse-phase, ion-exchange or ion-exclusion mechanisms.
The amount of the acid in the mobile phase influences the retention attributed to the ion-exchange interaction to the same degree as the organic modifier affects the retention in reverse-phase separation. Thus, the amounts of organic and acidic modifiers are both important for control of retention of ionizable analytes.
In addition to hydrophobic interactions, neutral compounds participate in different polar interactions with highly polar column functional groups. The behavior of polar groups can be modified by varying the mobile phase.
Basic functional groups on Primesep B column form salts with different acid residue (sulfate, perchlorate, trifluoroacetate, etc.), and each salt participates differently in polar interaction with neutral analytes. Analytes themselves can be ionized in many ways depending on the pH of the mobile phase, and retention time of your compounds can also be substantially altered by changing the pH of the mobile phase.