Synthesis and characterization of novel internal surface reversed-phase silica supports for high-performance liquid chromatography

An original synthetic method was developed for the preparation of a family of six novel deactivated restricted-access materials (RAMs), belonging to the group of the internal surface reversed-phase (ISRP) supports. The supports (ISRP-RAM phases A–F) have an alkyl-chain (14 methylenes) with two embedded ureido groups bound only to the internal surfaces of the porous silica, and polyvinyl alcoholic groups (PVA, 100 000 → 22 000 molecular weight) chemically bound to the external surfaces. The average pore diameters of the prepared ISRP-RAM supports, calculated by inverse size-exclusion chromatography, ranged between 49 Å and 88 Å, and were able to exclude macromolecules heavier than about 24 000 Da (such as serum proteins) from the pores. The novel supports were designed for the determination of a semi-synthetic anticancer drug of the camptothecin family in human plasma, but they represent universal ISRP-RAM supports not limited to such class of compounds.