Synthesis and evaluation of a ferrocene-bonded silica phase for reversed-phase high-performance liquid chromatography

The preparation, characterization, and potential liquid chromatographic applications of a ferrocene-bonded silica stationary phase are presented. The phase was prepared by covalent bonding of ferrocene-derivatized aminosilane to silica gel then end-capping with trimethylchlorosilane. Use of the new stationary phase enabled good separations of alkylbenzenes, halobenzenes, polycyclic aromatic hydrocarbons, and even basic compounds under reversed-phase conditions. The linear relationship between log k (where k is the retention factor) and the number of pi electrons (n(pi)) in the structures of polyaromatic hydrocarbons indicates that the mechanism of retention on the new stationary phase involves strong pi-pi interaction with one of the cyclopentadienyl (Cp) groups of the ferrocene. The retention increment for a methylene group was calculated. The value indicates that the mechanism of retention on the new stationary phase also involves a strong hydrophobic interaction, so the phase enables effective separation of compounds with a benzene ring.