Page 148 - Applied Pharmacognosy
P. 148
Mobile Phase Selection
Guidelines for Setting Mobile Phase Conditions
❑ If the sample is cationic i.e. basic:
Reversed phase mode is still an option…. But
❑ Mobile Phase Strength has to be adjusted by changing Eluent
Composition to be: Acidic buffer solution containing anions
with a low charge density (e.g., perchlorate ions) or Alkyl
Sulfonic Acid / Acetonitrile or Methanol.
Making eluent acidic
→ Suppresses dissociation of residual silanol groups
→ Prevents tailing!
Adding perchlorate ions
→ Forms ion pairs → Increases retention strength!
→ Suppresses tailing! 147
