Edivan Tonhi

Fases estacionárias para cromatografia líquida de alta eficiência em fase reversa (CLAE-FR) baseadas em superfícies de óxidos inorgânicos funcionalizados

Particles of porous silica or other solvent resistent inorganic oxides can be functionalized by aliphatic (e.g., C-8 or C-18) or other groups to give stationary phases for use in reversed phase HPLC. The functionalization can be done by bonding of individual groups to the surface of the support particles, by producing an organic polymeric film from pre-polymers, or by adsorbing/immobilizing pre-formed polymers on the surfaces. These three types of functionalization are reviewed.

Obtenção e caracterização de blendas colágeno-quitosana

Biodegradable polymer blends were obtained using collagen and chitosan. Membranes of collagen and chitosan in different proportions (3:1, 1:1 and 1:3) were prepared by mixing their acetate solutions (pH 3.5) at room temperature. The blends were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier Transform infrared (FTIR) spectroscopy, specific viscosity, water absorption and stress-strain assays. The results showed that chitosan did not interfere in the structural arrangement of the collagen triple helix and the properties of the blends can be controlled by varing the proportion of the collagen and the chitosan.

High-performance liquid chromatographic stationary phases based on poly(methyloctylsiloxane) immobilized on silica: I. Physical and chemical characterizations

Five different reversed-phase materials for high-performance liquid chromatography were obtained by deposition of poly(methyloctylsiloxane) in HPLC silica particles, followed by immobilization using different processes: thermal treatment (120 or 220 degrees C for 4 h), irradiation with microwaves (495 W for 15 min), gamma radiation (dose of 80 kGy) and self-immobilization. These phases were characterized by gel permeation chromatography, percent carbon, 13C and 29Si solid-state nuclear magnetic resonance spectroscopy, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The results show that the different immobilization processes produce different physical characteristics in the prepared phases.

High-performance liquid chromatographic stationary phases based on poly(methyloctylsiloxane) immobilized on silica II. Chromatographic evaluation

This work describes the chromatographic characterization of stationary phases prepared by deposition of poly(methyloctylsiloxane) (PMOS) on silica followed by immobilization using one of several different processes: thermal treatments (120 or 220 degrees C for 4 h), microwave irradiation (495 W for 15 min), gamma radiation (dose of 80 kGy) or self-immobilization. This evaluation was based on the chromatographic parameters of several test solutes. The stationary phases immobilized at 220 degrees C and which underwent self-immobilization were not appropriate for chromatographic use but the other immobilized phases presented chromatographic performances similar in most respects to a commercial phase (Rainin C8) while the peak characteristics of the basic probe were significantly better with these phases.

High-performance liquid chromatographic stationary phases based on poly(methyloctylsiloxane) immobilized on silica: III. Stability evaluations

Several reversed-phase materials for high-performance liquid chromatography were obtained by deposition of poly(methyloctylsiloxane) (PMOS) on HPLC silica particles, followed by immobilization using different procedures. Each phase had characteristic physicochemical and chromatographic properties. The present work evaluates the stability of these phases with both neutral and basic mobile phases. All of the stationary phases were quite stable to neutral mobile phase, with less stability at higher pH. However, one thermally immobilized phase presented high stability even at an elevated temperature with a pH 10.0 mobile phase.

High-performance Liquid Chromatographic Stationary Phases Based On Poly(methyloctylsiloxane) Immobilized On Silica I. Physical And Chemical Characterizations

Five different reversed-phase materials for high-performance liquid chromatography were obtained by deposition of poly(methyloctylsiloxane) in HPLC silica particles, followed by immobilization using different processes: thermal treatment (120 or 220 degrees C for 4 h), irradiation with microwaves (495 W for 15 min), gamma radiation (dose of 80 kGy) and self-immobilization. These phases were characterized by gel permeation chromatography, percent carbon, 13C and 29Si solid-state nuclear magnetic resonance spectroscopy, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The results show that the different immobilization processes produce different physical characteristics in the prepared phases.

High-performance liquid chromatographic stationary phases based on poly(methyloctylsiloxane) immobilized on silica

Five different reversed-phase materials for high-performance liquid chromatography were obtained by deposition of poly(methyloctylsiloxane) in HPLC silica particles, followed by immobilization using different processes: thermal treatment (120 or 220 degrees C for 4 h), irradiation with microwaves (495 W for 15 min), gamma radiation (dose of 80 kGy) and self-immobilization. These phases were characterized by gel permeation chromatography, percent carbon, 13C and 29Si solid-state nuclear magnetic resonance spectroscopy, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The results show that the different immobilization processes produce different physical characteristics in the prepared phases.