Page 134 - Applied Pharmacognosy

Mobile Phase Selection

How to adjust the Mobile phase Strength?

❑ Mobile Phase Strength is adjusted by changing:
➢ Type of Modifier (MeOH, ACN).
➢ Solvent Strength (% modifier), has a greater

influence on separation.
➢ pH if buffer is used (falls within the

recommended pH limits for the used column.)

➢ Type of Buffer (phosphate, acetate).

➢ Ionic Strength (Salts, buffer concentration).

➢ Ion-Pairing Reagents (alkylamines,

sulfonates).

❑ Ensure that the ionizable functional group is in a

single form. E.g. Reduce peak tailing for basic

compounds by masking the silanols. 133