Biomedical subjects

Kenneth E Collins

Publications and source records attributed to Kenneth E Collins.

23 records · Page 2Linked to original sources

PubMed2003

Preparation of a polybutadiene stationary phase immobilized by gamma radiation for reversed-phase high-performance liquid chromatography.

Polybutadiene (PBD) has been immobilized on HPLC silica by gamma radiation doses in the range from 5 to 180 kGy. Columns prepared from these reversed-phase materials, as well as from similar non-irradiated materials, were tested with standard sample mixtures and characterized by elemental analysis (% C) and infrared spectroscopy. A low dose of 5 kGy is sufficient to produce a layer of immobilized PBD which functions as an efficient and stable stationary phase. Higher doses give thicker immobilized layers having less favorable chromatographic properties.

Butadienes↗

PubMed2003

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.

Chromatography, High Pressure Liquid↗

PubMed2002

Poly(alkylmethylsiloxanes) thermally immobilized on silica as stationary phases for high-performance liquid chromatography.

Poly(methyloctylsiloxane) (PMOS) and poly(methyloctadecylsiloxane) (PMODS) were sorbed onto porous HPLC silica and thermally immobilized, in the absence of radical initiators, at temperatures in the range of 80 to 180 degrees C. Following extraction of non-immobilized polymer the materials were packed into columns and their chromatographic properties evaluated. The shorter chain (PMOS) stationary phase showed good HPLC characteristics after thermal immobilizations up to 120 degrees C while the longer chain (PMODS) phase gave satisfactory HPLC phases following thermal immobilizations at 80 and 100 degrees C. Stability evaluation for the PMOS and PMODS columns immobilized at 100 degrees C required 250 ml of pH 8.5 mobile phase at 60 degrees C to significantly decrease efficiency, suggesting a long useful life time at neutral pH and ambient temperature.

Algorithms↗

PubMed2002

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.

Carbon Isotopes↗

PubMed2002

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.

Carbon↗