The Cogent UDA™ HPLC column ligand is a C11 chain with a carboxylic acid on one end. On the other end, there are two orientations for how the ligand could be bonded to the Cogent TYPE-C™ Silica support. The first orientation is shown in A. In this case, only one hydro-silation occurs from the starting reagent, resulting in a remaining double bond and a single point of attachment. In the second orientation B, another hydro-silation occurs with structure A and a nearby Si-H group, resulting in no more double bonds.

This requires that the other Si-H group is close enough to react. This is called a Bidentate attachment. For the Cogent UDA™ HPLC columns, B is structure of the ligand.