Amphoterics loss of liberated ions

WS and SW amphoterics may not always yield the expected number of hydrogen or hydroxide ions. The circumstances in which this may occur are as follows. A WW amphoteric is represented for simplicity as NH -----COO . 

Acidic column, WW in zwitterionic or anionic (fully deprotonated) form, WS in zwitterionic form. The liberated proton may be captured by a carboxylate group and so be retained in the resin. For example, 

In the case of the WW in the anionic form, it is actually the accompanying cation that displaces a hydrogen ion from the resin, not the amphoteric itself. The end result is the same. 

The hydrogen ion cannot be lost when the amphoteric is in the fully protonated form. 

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