Inorganic packing

Eor a long time there have been discussions about which type of sorbent is the best for SEC separations in various mobile phases. In principle, organic (copolymer) and inorganic packings can be used. Each type of packing has its benefits and drawbacks. Table 9.3 summarizes major sorbent properties and reveals some interesting aspects of SEC separations and its requirements on packings. 

Inorganic packings (silica, alumina, etc.) are very stable (yet brittle) and show very high pore volumes (i.e, efficiency). However, their chemical stability is very limited and the surface is very active (this is also true for reversed-phase columns), allowing their use in special applications only. 

Table 3.5 Survey of the generic types of inorganic packings for chromatography and their characteristic properties.

The excellent mechanical stability that inorganic gels exhibited led to the development of microporous silica and glass particles for polymer separations with both aqueous and organic eluents. Columns of inorganic packings can be used at... 

Other Surface Modification Tediniques for Inorganic Packings... 

When the behavior of inorganic packings is studied in detail, it is found that the primary parameter that determines a particle s strength is the specific pore volume. Particles with a high pore volume break more easily than do particles with a small pore volume. However, since the pressure per unit length in most chromatographic applications rarely exceeds 2 MPa/cm, the commonly used particles with a pore volume of 1 mL/g are of sufficient strength. 

In Section 6.4, we will investigate other surface modification techniques that have been developed for inorganic packings and do not rely on the attachment of the interacting layer to the surface of the packing. This area of HPLC technology is still in flux, and new technical developments can be anticipated. 

OTHER SURFACE MODIFICATION TECHNIQUES FOR INORGANIC PACKINGS... 

OTHER SURFACE MODmCATION TECHNIQUES FOR INORGANIC PACKINGS 127... 

Heats of adsorption, — varied directly with the -electron density of the adsorbates and inversely with the number of 3d electrons of the inorganic packings (sorbents). 

Thermodynamics provided the theoretical and experimental framework for judging the characteristics of the sorbates and generalizations concerning the nature of the interactions observed. For example, van t Hoff plots (In Vg versus 1/T) were employed to calculate the heats of adsorption (—A fads) of the individual sorbates on the various inorganic packings(sorbents). In the practice of GSC, another measurement of the sorbent is its surface area. A number of techniques are available to obtain measurements of the surface area (36,37). 

Inorganic packing material Mature compost 1700 gm y 720 g m2 d" 360 g m2d" Laboratory experiment. Active aeration Maximum values Niekiema et al. (2005)... 

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