“Base-deactivated” means that the Column is designed for analysis of Basic Compounds. Conventional Columns Based on Type B Silica typically have Si-OH groups on the surface that interact with bases. This Secondary Retention Mechanism is typically Undesirable and causes poor Peak Shapes. The following are two ways that Reversed Phase HPLC columns can get around this:
1) They “end-cap” the material. This is where they react the Si-OH groups with a small organic functional group, which does not interact with bases like Si-OH groups do. The problem with this method is that the end-capping groups are susceptible to hydrolysis over time. Therefore, the chromatography of the column may change over time as these groups are hydrolyzed.
2) They use a “polar embedded” group. This is where the organic ligand (e.g. C18) has an amide (—CO—NH—) group near the beginning of the chain. What this means is that the amide hydrogen-bonds with nearby Si-OH groups and thereby reduces their activity towards bases.
As a third approach, our Cogent TYPE-C Silica™ columns are made such that the Si-OH groups are replaced with a stable layer of Si-H surface which does not adsorb water. Si-H is not acidic and therefore does not contribute to basic peak tailing.