Per-Aqueous Liquid Chromatography for the Separation of Polar Compounds-Preparation and Characterization of Poly(ethylene oxide-co-dimethylsiloxane) Based Stationary Phase

Abstract

Poly(ethylene oxide-co-dimethylsiloxane) was thermally immobilized on silica particles- Si(PEO)-to separate small polar compounds with water-rich mobile phases. Poly(ethylene oxideco- dimethylsiloxane) content on Si(PEO) stationary phase was optimized using a central composite design. Infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis morphologically and structurally characterized the optimized material. Separation of standard test mixtures showed that the Si(PEO) phase had a typical reversed-phase elution order. However, the Si(PEO) phase retained polar compounds better than C18 or aqueous C18 phases under waterrich mobile phases. Under this condition, small changes in the acetonitrile fraction resulted in a marked increase in the retention of some polar drugs on the Si(PEO) phase. A typical condition observed in per aqueous liquid chromatography separations, a more environmentally friendly liquid chromatography approach. On the other hand, hydrophobic compounds showed lower mass transfer rates due to their low solubility in the aqueous mobile phase. Thus, the Si(PEO) phase was more suitable and efficient for separating polar or hydrophilic compounds.