Preparation and characterization of a poly(methyloctadecylsiloxane) thermally immobilized onto zirconized silica stationary phase for high-performance liquid chromatography

Facile synthesis of zirconia-coated mesoporous silica particles by hydrothermal strategy under low potential of hydrogen conditions and functionalization with dodecylphosphonic acid for high-performance liquid chromatography

In this work, multilayer zirconia-coated silica (ZrO₂/SiO₂-n) microspheres were successfully produced by a straightforward hydrothermal procedure with a low concentration of Zr⁴⁺ (5 mM) under low potential of hydrogen (pH) conditions (pH = =2). The obtained ZrO₂/SiO₂-n materials exhibited favorable characteristics for high-performance liquid chromatography (HPLC) separation, including high surface area and pore volume, good pore structure, narrow particle size, and pore size distribution. In addition, the zirconia coverage in the mesopores was confirmed by soaking the material in 1 M NaOH solution, with the particles showing strong resistance to the basic solution. The obtained ZrO₂/SiO₂-n stationary phases were packed into a fused-silica capillary tubing for the separation of alkaloids in hydrophilic interaction chromatography (HILIC) mode, and a column efficiency of 47,800 plates/m was obtained for berberine on a ZrO₂/SiO₂-6 micro column. The ZrO₂/SiO₂-6 microspheres were further modified by dodecylphosphonic acid (C₁₂P-2-ZrO₂/SiO₂-6); the C₁₂P-2-ZrO₂/SiO₂-6 material showed great potential for application in reversed-phase liquid chromatography (RPLC) mode. The C₁₂P-2-ZrO₂/SiO₂-6 micro column showed a column efficiency of 55,000 plates/m for naphthalene and 51,300 plates/m for benzene.

In vitro drug release and ex vivo percutaneous absorption of resveratrol cream using HPLC with zirconized silica stationary phase

Since the designs of optimal formulations for resveratrol permeation via the skin are lacking, the aim of this study was to establish the profile of resveratrol permeability into and across human skin. For that, a laboratory-made chromatographic column was used (Zr-PMODS), with its performance being compared to a traditional C18 column. In vitro drug release was conducted with polysulfone membranes, and the flux (JS) was 30.49 μg cm(-2) h(-1)), with a lag time (LT) of 0.04 h, following a pseudo-first-order kinetics. For ex vivo percutaneous absorption using excised female human skin, the kinetic profile was the same, but JS was 0.87 μg cm(-2) h(-1) and LT was 0.97 h. From the initials 49.30 μg applied to the skin, 9.50 μg were quantified in the receptor medium, 20.48 μg was retained at the stratum corneum (do not account as permeated) and 21.41 μg was retained at the viable epidermis+dermis (account as permeated), totalizing 30.90 μg of resveratrol permeated after 24 h of application (62.6%). From these results, one can conclude that a person using the 1-g emulsion dose released by the pump containing 20mg of resveratrol will have, theoretically, 12.53 mg of it liberated into his bloodstream, gradually and continuously for 24 h.