These carboxylic acid HPLC columns have a silica hydride surface similar to other TYPE-C™ Silica phases but the uniqueness of Cogent UDA™ is that they can exhibit weak cation exchange properties in addition to RP and ANP retention; a mixed mode is possible with some mobile phases conditions.
A terminal carboxylic acid group contributes some additional selectivity in this column and when the mobile phase is above pH 5,9, the acid group becomes 90% negatively charged and at pH 6,9 is 99% charged and may act as a cation exchanger. Below pH 4,9, the group does not have significant ion exchange properties.