Analyte: Weak Anion, pKa 5.0       R-COOH      R-COO-      R-COO- 

          Sorbent: NH2, pKa 9.8           R-NH3+     R-NH3+ R-NH2

Analyte: Strong Anion                       R-SO3-          R-SO3-       R-SO3-

             Sorbent: NH2, pKa 9.8           R-NH3+     R-NH3+ R-NH2

pH 3
pH 7
pH 11
Weak Anion Exchange (NH2)