Page 139 - Applied Pharmacognosy
P. 139
Mobile Phase Selection
Guidelines for Setting Mobile Phase Conditions
❑ The second case scenario; if sample is ionic (cationic or
anionic) and not any of the previously mentioned exceptions:
Reversed phase mode is still an
option…. But
❑ Mobile Phase Strength has to be adjusted by changing:
➢ 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).
In the analysis of ionic solute, the pH value of the eluent
greatly influences the retention strength 138
