What is the difference between weak and strong cation exchange for Ion Exchange columns – FAQ

An HPLC stationary phase is considered a weak cation exchanger when it has a functional group such as a carboxylic acid which proton does not come off (ionize) until around pH 4 or so.  

Columns with sulfonic acid groups for example, are considered strong cation exchangers because they are essentially un-protonated (ionized) at any reasonable mobile phase pH for HPLC.