Stationary phase properties

Solvent selectivity is seen as the factor that distinguishes individual solvents that have solvent strengths suitable for separation. In reality, separations result from the competition between the mobile and stationary phases for solutes based on the differences of all intermolecular interactions with the solute in both phases. Solvents can be organized on selectivity scales that are useful for initial solvent selection, but in a chromatographic separation the properties of the stationary phase must be taken into consideration. Methods that attempt to model chromatographic separation need to consider simultaneously mobile and stationary phase properties [38]. 

Dittmann, M. M., and Rozing, G. P. (1997). Capillary electrochromatography investigation of the influence of mobile phase and stationary phase properties on electroosmotic velocity, retention, and selectivity. J. Microcolumn Sep. 9, 399-408. 

In the following discussion we attempt to shed light on some of the stationary phase properties, which in view of Eqs. (7) and (8) affect the magnitude of the retention factor in RPC. ... 

Pacholec, F., and Poole, C.F., Stationary phase properties of the organic molten salt ethylpyridinium bromide in gas chromatography, Chromatographia, 17, 370-374,... 

Solute descriptors are available for more than 2,000 compounds. The magnitude of the coefficients is due to a difference between mobile and stationary phase properties. According to Sny-... 

Influence of the Stationary Phase Properties on SMBR Efficiency... 

In the following section, an example is discussed to illustrate how the most important stationary phase properties - namely, sorption selectivity, sorption capacity, and catalytic activity - affect the SMBR performance. 

Before proceeding with a discussion on the individual modes of separation it is worth reviewing a brief glossary of terms in association with the stationary phase properties. A simple strategy for selection of the stationary phase will naturally follow, in order to help the reader to choose a supplier wisely. 

Stationary Phase Properties. Column stability requires that the stationary phases be bonded to the column wall (OT) or the solid support (packed). 

As we discussed above, efficiency and selectivity are complementary descriptors dependent on the different sets of chromatographic parameters. Efficiency is more dependent on the quality of the column packing, particle size, flow rate, and instrumental optimization, while selectivity is more dependent on the stationary phase properties and the nature of the analytes themselves. However, efficiency is sometimes affected by nonideal interactions of the analyte with the stationary phase (i.e., peak tailing). 

The usual A solvent in reversed-phase chromatography is water or aqueous buffer. The strength of binary mixtures is not a well defined function of %B but depends on analyte and stationary phase properties. Nevertheless, it is possible to give numerical... 

An optimised chromatographic separation is achieved by varying the mobile and stationary phase properties and operating parameters to give the required retention of the components in a sample. The overall retention characteristics for each component are related to the kinetics and mass transfer processes, leading to retention forces. 

Prototypical solutes used by McReynolds (Rorschneider solutes in parentheses) to characterize stationary phase properties... 

Mobile phase modifications of stationary phase properties, that are also expected to vary with density, are a further complication [90-96]. The supercritical fluid... 

Resolution of the protein separation is affected by several stationary phase properties. Reduction of the particle diameter is obviously the most straightforward way to improve the efficiency. For analytical purposes, 3- to 10-pm particles are a good compromise between chromatographic performance and the required pressure. The pore size of the particles should be a minimum of 300A to provide accessibility for large proteins. 

Retention of neutral molecules is almost not affected by buffers and mobile phase pH. Optimization options are limited to stationary phase properties and mobile phase solvent composition. 

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