NUCLEODUR^® – C18 Pyramid

Polar compounds such as carboxylic acids, and drug metabolites only show weak retention on densely bonded reversed-phase columns from distinct hydrophobic properties but low polar interactions.

Very polar analytes require highly aqueous mobile phases for solubility and retention.

Conventional reversed-phase columns often display stability problems in eluent systems with a high percentage of water (> 95%) as evidenced by a sudden decrease of retention time and overall poor reproducibility.

This phenomenon is described as phase collapse caused by the mobile phase expelled from the pores due to the fact, that hydrophobic RP phases are incompletely wetted with the mobile phase.

Different approaches can be used to increase column stability with highly aqueous mobile phase systems. The most promising are incorporating a polar group in the hydrophobic alkyl chain, or using hydrophilic endcapping procedures to improve wettability of the reversed-phase modification.

NUCLEOSIL Nautilus may be taken as an example for the embedded polar group strategy, in which a C18 silane with a polar function is successfully linked to the silica surface.