Packed columns stationary phase solvation

The master retention equation of the solvation parameter model relating the above processes to experimentally quantifiable contributions from all possible intermolecular interactions was presented in section 1.4.3. The system constants in the model (see Eq. 1.7 or 1.7a) convey all information of the ability of the stationary phase to participate in solute-solvent intermolecular interactions. The r constant refers to the ability of the stationary phase to interact with solute n- or jr-electron pairs. The s constant establishes the ability of the stationary phase to take part in dipole-type interactions. The a constant is a measure of stationary phase hydrogen-bond basicity and the b constant stationary phase hydrogen-bond acidity. The / constant incorporates contributions from stationary phase cavity formation and solute-solvent dispersion interactions. The system constants for some common packed column stationary phases are summarized in Table 2.6 [68,81,103,104,113]. Further values for non-ionic stationary phases [114,115], liquid organic salts [68,116], cyclodextrins [117], and lanthanide chelates dissolved in a poly(dimethylsiloxane) [118] are summarized elsewhere. 

System constants derived from the solvation parameter model for packed column stationary phases at 121°C... 

The system constants for packed column stationary phases are summarized in Table 8. Classification of their properties by cluster analysis results in the connection dendrogram shown in Figure 4. Stationary phases with similar solvation properties are located next to each other and connected close to the left-hand side of the dendrogram. Stationary phases with no paired descendents are singular phases with properties that cannot be duplicated by other phases from the data set (Table 8). Classification results in six groups with three phases behaving... 

Elution of a particular compound in SFC is a function of its extent of interaction with the column stationary phase and the solvating strength of the mobile phase, with the latter being a direct function of density. The density is affected by temperature and pressure and, in the case of separations with capillary columns that are inherently open and exhibit little pressure drop across their length, it is essentially constant throughout. By contrast, packed columns exhibit much more resistance to mobile-phase flow and can experience a considerable density drop during SFC... 

In a GPC experiment, the polymer is separated in a column which is filled with a swollen, uniformly packed resin ( gel , called stationary phase, while the solvent which passes through the column is called mobile phase). The gel beads are usually made of crosslinked polymers (in particular polystyrene but also various inorganic porous materials) with little holes and pores of different size where the pore diameter is of the dimension of the size of the solvated polymer coils, i.e., the pore-size distribution is approx. 10-10 nm. 

The column can be an open capillary or a packed tube. In the first case the mobile phase is coated as a thin film on the inner wall of the capillary. If the mobile phase has a certain solvating power, as in SFC, it is necessary to cross-link this liquid film, whereas in GC linear polymers are used in many cases because the usual carrier gases, helium and hydrogen, cannot dissolve any stationary phase. (Owing to problems with manufacturing and... 

The stationary phase can be inside a tube as a packing or a thin layer (column chromatography) or on a flat surface. The interactions of the components of the mixture depend on the nature of the stationary phase. Adsorption on surfaces, solvation in a liquid layer or solid layer (membrane), and reversible chemical reaction between ionic parts of molecules are examples of interaction mechanisms. 

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