In HPLC method development, what is the typical approach to mobile phase pH for ionizable compounds, and what are the implications for retention and peak shape?

In HPLC method development, what is the typical approach to mobile phase pH for ionizable compounds, and what are the implications for retention and peak shape?

• A. For acids, pH below their pKa to keep neutral and more retained; for bases, pH above their pKa to keep neutral and more retained; also avoid pH near silica pKa to minimize tailing and column damage.
• B. For acids, always set pH to 7; bases to 7 as well.
• C. Set pH to maximize ionization for both acids and bases.
• D. pH has no effect on retention.

Answer: (A)