SIMPLE PREPARATION OF A C-8 HPLC STATIONARY-PHASE WITH AN INTERNAL POLAR FUNCTIONAL-GROUP

A novel HPLC stationary phase is described that possesses an internal carbamate functional group. The reversed-phase material is prepared via bonding of silica with 3-(chlorodimethylsilyl)propyl N-octylcarbamate, which is prepared in two steps from octylamine and allyl chloroformate. The resultant bonded silica has a reproducible ligand surface concentration of 3.2-3.3 mu mol/m(2). The methodology is an alternative to the reaction of acid chlorides with aminopropyl bonded phases, where an inhomogeneous mixture of derivatized and underivatized amine groups results. The chromatographic properties of the octylcarbamate bonded phase were compared to those of an end-capped octyldimethylsilyl bonded phase using a variety of neutral, acidic, polar, and basic compounds under different mobile-phase conditions. The octylcarbamate phase exhibited dramatically reduced retentions for polar and basic compounds. The reductions are attributed to the embedded carbamate group's weakening of the interaction between unbonded silanols and the analytes.