Stationary Phase Immobilization Research Articles

Нанесение неполярных силиконовых неподвижных фаз на поликапиллярные колонки с использованием золь-гель метода

Высокоэффективные поликапиллярные колонки (ПКК) с иммобилизованными неподвижными фазами (НФ) получены нанесением на многоканальные трубки (МКТ) неполярных полисилоксанов PS 347.5 и SE-54 динамическим способом с использованием золь-гель технологий. При применении свежеприготовленного золь-геля степень иммобилизации НФ составляет более 86%. Полученныеколонки демонстрируют повышенную термостойкость и пониженный уровень фона, вызванный уносом НФ

Sol−Gel Column Technology for Single-Step Deactivation, Coating, and Stationary-Phase Immobilization in High-Resolution Capillary Gas Chromatography

A sol−gel chemistry-based novel approach to column technology for high-resolution capillary gas chromatography is described that effectively combines surface treatment, deactivation, coating, and stationary phase immobilization into a single step. In the conventional approach, these operations are carried out in separate steps that make column fabrication a time-consuming job. In the new approach, a cleaned fused silica capillary is filled with a sol solution of appropriate composition, and sol−gel reactions are allowed to go on inside the capillary for a controlled period, typically 15−60 min. A wall-bonded coating results due to condensation of the surface silanol groups with the sol−gel network evolving in their vicinity. Because of the direct chemical bonding to fused silica substrates, sol−gel coatings possess significantly higher thermal stability than conventional coatings. This is especially important for thick and/or polar stationary phase coatings that are difficult to immobilize. Scanning elect...

Column packings with immobilized methyl polysiloxane phases for gas chromatography

The free radical cross-linking procedure of stationary phase immobilization introduced by Grob et al. for capillary columns has been adapted for the preparation of column packings on diatomaceous supports. Immobilization of SE-30 and OV-1 on typical gas chromatography supports: Polsorb B-AW, Chromosorb W-AW, Chromosorb G-AW and Gas Chrom Q was investigated. Before immobilization, the supports (excluding Gas Chrom Q) were purified by extraction with 6 M HCl in a Soxhlet extractor and silanized with hexamethyldisilazane vapour at 300°C. The influence of the type and concentration of peroxide on the efficiency of immobilization of the silicone was studied. In order to obtain over 95% immobilization a minimum of 2% w/w of the peroxide in the stationary liquid is required. Properties of packings with immobilized phase were compared with those of related conventional packings. Adsorption activity, column efficiency and thermal stability were used for this comparison.

Current aspects of stationary phase immobilization in open tubular column chromatography

AbstractIn situ stationary phase immobilization in principle can be attempted in two different ways: using thermal methods or radical‐initiated reactions. Thermal immobilization, in general, is applied for the preparation of columns to be used at ultra‐high temperatures, and radical‐initiated immobilization can be applied in most other cases. For polar, narrow‐bore, and thick‐film columns, low immobilization temperatures are preferred. The reactions involved in the different immobilization methods are described in this review, and the advantages and disadvantages of current immobilization methods are discussed.

Effect of repeated cross-linking of SE-54 stationary phase film on the chromatographic properties of capillary columns

The effects of repeated cross-linking of SE-54 stationary phase with azo- tert.-butane on the degree of stationary phase film immobilization and on the chromatographic properties were studied. The optimum numbers of repeated immobilizations in the columns for gas and liquid chromatography were determined. Excessive repetition of immobilization adversely affected the chromatographic properties. The contribution of chemical bonding to the degree of stationary phase immobilization was studied with capillaries silylated with octamethylcyclotetrasiloxane.

Evaluation of an immobilized cyanosilicone, 60-CN, as a stationary phase for capillary gas chromatography

The influence of several factors, such as the method used for the synthesis of the stationary phase, the type of fused-silica capillary tubing, surface deactivation, stationary phase immobilizatioin, column rinsing and ageing, on the properties of capillary columns coated with silicones having 60% cyano substitution has been investigated. The column properties studied were efficiency, deactivation, acid base status, polarity and thermal stability. The column properties were found to be generally improved by stationary phase immobilization. However, an increase in the HETP of n-alkanes is a disadvantage that may be encountered. Well deactivated, relatively efficient columns were prepared with good reproducibility. The properties were largely retained after column ageing at 220°C.

A two‐step method for the immobilization of stationary phases in GC capillary columns

A two‐step method for the immobilization of stationary phases in GC capillary columns

Capillary columns with immobilized stationary phases : II. Practical advantages and details of procedure

Experimentally demonstrated advantages of stationary phase immobilization are considered, namely, prevention of thermal rearrangement, prevention of phase stripping, sharper peaks of solvent and major sample components, regeneration of columns by solvent washing, thick films produced from fluid phases, low bleeding rates, easy recoating and repeated coating to produce sandwich coatings. The cross-linking reaction which produces an immobilized stationary phase is strongly dependent on the structure of the stationary phase. OV-61 is representative of stationary phases having the maximum polarity allowing immobilization. The polarity limit will probably be shifted to higher values. Immobilization as a method of producing stable coatings on difficult to wet support surfaces is limited to support-stationary phase combinations providing nearly perfect wettability. The selection of a suitable peroxide for the cross-linking reaction is discussed. Based on arguments such as activity, cross-linking efficiency, influence of decomposition products, volatility, stability in solution, and safety of handling, a clear preference for a dialkyl peroxide, e.g., dicumyl peroxide, is indicated. Appropriate peroxide concentrations are discussed, and detailed instructions for the immobilization procedure are given. Particular attention is paid to solvent washing of the immobilized stationary phase columns.