A novel reversed-phase and weak anion-exchange mixed-mode stationary phase based on horizontal polar-copolymerized approach for separation of small organic molecules and inorganic anions.

A novel silica-based reversed-phase/weak anion-exchange mixed-mode chromatography (MMC) stationary phase referred to as OTAS was synthesized based on the horizontal polar-copolymerized approach using trichlorooctadecylsilane (ODS) and (3-glycidyloxypropyl)trimethoxysilane (GPS) as ligands, and then followed by the reaction of epoxy group with diethylamine to introduce the tertiary ammonium functional group. The new stationary phase was characterized by instrumental analysis, and evaluated by separating the mixture of alkylbenzene homologues in reversed-phase mode and acidic organic compounds in ion-exchange chromatography mode, respectively. The results indicate that not only the baseline separation of 11 kinds of neutral and acidic organic compounds can be achieved successfully, but also 5 kinds of inorganic anions can be separated completely. The chromatographic property of OTAS column can be controlled by adjusting the molar ratio of ODS to GPS. Moreover, the OTAS column was used successfully to analyze the inorganic anions in the actual water samples. The good separation and selectivity of OTAS column suggests that the new MMC stationary phase can be used for the analysis of complex samples containing of neutral and acidic organic compounds or inorganic anions.