Capacity Of Stationary Phase Research Articles

Preparation and characterization of open tubular ion chromatographic columns

In recent years, significant progress has been made in the area of open tubular ion chromatography (OTIC). In particular, gradient OTIC has been realized through the development of hydroxide eluent-compatible OTIC columns. This review covers the preparation and characterization of different OTIC columns, ranging from the historic silica-based columns to the newly emerging polymer-based open tubular (OT) columns. The preparation of various OTIC stationary phases, from grafted to latex agglomerated and monolayer to multilayer phases, has been briefly introduced. The characterization of electrostatic latex agglomerated OTIC columns has been extensively discussed, e. g. fluorescent ion displacement chromatography, frontal displacement chromatography, and frontal reaction chromatography have been used to measure the capacities of OT columns, and the results are compared with the theoretical calculation values. The variable αiex, defined as the number of ion-exchange equivalents per unit surface area, is used as an indicator of the capacity of OT columns, to enable a straightforward comparison between OT columns having different inner diameters (i.d.). The newly introduced column capacity parameter, γiex, defined as the stationary phase capacity per unit liquid volume present, is used to investigate the relationship between packed and OT columns when using the same stationary phase. Methods for improving the column efficiency, such as decreasing the column diameter and/or increasing the column temperature, are presented. In addition, determination of the functionalization uniformity along an OT column by (a) separately measuring the capacities of two halves of the column, (b) measuring the retention factors for several ions in successive 10 cm segments of the column in multiple injections, and (c) measuring the retention variance of a single ion in different segments of the column from a single injection, is discussed.

Analysis of the information in a preparative chromatogram for further optimization of the operating conditions

It was demonstrated how the most salient theoretical aspects of linear and non-linear elution liquid chromatography can be used, without the aid of sophisticated optimization software, to analyse the information in a preparative chromatogram. It is important. First, to be able to recognize whether a given preparative chromatogram was obtained under volume- or mass-overload conditions or both. This permits further optimization of the injection conditions (size, volume and concentration of the sample), depending on the preparative objectives, and improvement of the stationary phase particle size and of the mobile phase flow-rate. This approach can also provide insight into the performance characteristics of the injection device, the efficiency of the column packing and the stationary phase capacity. Some examples taken from the recent literature are discussed.