Similar Selectivity to C18 Columns | Bidentate C8 is Unique | Range of Particle Choices
C8 columns differ from C18 columns in that they are less dense and that decreases the surface area of the phase and the mass transfer. Being less dense the C8 columns are less hydrophobic and will have similar selectivity compounds but retain them for less time than a C18.
Another feature of C8 columns is that they may be able to retain some slightly polar compounds that C18 cannot retain very well.
TYPE-C™ Silica is the unique "silica-hydride" that has a double point of attachment of the C8 ligand with direct silicon-carbon bonds, no end capping is needed. This makes the Cogent Bidentate C8™ phase the most stable C8 on the market. The typical water shell that is found in other stationary phases allows for some very unique features including operation in ANP (Aqueous Normal Phase), NP (Normal Phase) or RP (Reversed Phase), and modes can be changed without hysteresis. This C18 column is very hydrophobic compared to most C18 columns.
Traditional Type-B, spherical, low metal content silica with exhaustive end-capping is the most commonly used column for Reversed Phase methods. These include the MOST POPULAR Cogent RP C8™ - Cogent HPS C8™ and other C8 columns including Similars™ C8 .
Irregular, Type-A silica bonded C18 with and without end-capping for older USP® monographs or in-house methods matches with the stationary phases used to develop the monographs. The Cogent MicroBee C8™ is made to be similar to µBondapak® C8.