Pellicular supports

A pellicular chromatographic packing consists of a rigid core with a relatively thick outer shell. The outer shell is cross-linked by the inclusion of a difunctional monomer and for added stability the outer shell may be covalently attached to the core. An example of this type of packing is the material developed for carbohydrate analysis, CarboPac (Dionex), which is a pellicular anion exchange resin bead which has a 5 pm non-porous sulphonated polystyrene bead core with a 0.1 pm quaternary amine latex. These materials have gained widespread acceptance for analytical separations and small-scale fractionations. 

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Both completely porous and pellicular supports (mainly of silica) consisting of spherical nonpo-rous particles covered with a very thin layer of porous adsorbents are used in peptide separations. A pore size of 100 A is commonly recommended for this purpose, but wider pore materials (300 A)... 

Partition coefficient, 9, 10 Partition ratio, 11 time optimization of, 57-58 Peak, definition of, 69 Peak capacity, 18, 19 Pellicular supports, 157 Permeability, 63-64 Phase selection diagrams, 218-219 Phase volume ratio, 11 Pinkerton (ISRP) columns, 225-226 Plate height, 17 Plate number, 14-16 Plate theory, 3, 28 Polarity index, 210, 211 Pore size of LC supports, 157 Porosity, 27 Precision, 99-100 Preparative scale ... 

An alternative method for achieving the effect of a small diameter is to coat a thin layer of porous solid on a solid core (such as glass). Such materials were widely used in the early days of LC and are usually called pellicular supports. Typically the porous layer is 1-2 pm thick, and the solid core has a diameter of about 40 pm. Pellicular solids are easier to pack than microporous solids, but they are less stable, have smaller capacities, and are more expensive. Since good packing methods are now known for the microporous solids, the pellicular solids have become much less popular. They are commonly used in guard columns (discussed later in this chapter). 

Guard Columns. To help protect analytical columns from degradation by dirty samples, it has become common to include a guard column between the injector and analytical column. These columns are short and intended to be discarded or repacked after they become contaminated. t Often they are dry packed with a pellicular support that is chemically... 

The mass transfer effects due to the diffusion into the intraparticle medium will be eliminated with nonporous supports 49.501. One can also use pellicular supports by immobilizing the protein on the external surface. This approach is possible (21-25] with silica adsorbents of small pore size (< 6 nm) because the large biomolecules of antibodies cannot penetrate into the pores of the support, and the immobilization takes place on the external surface of the particles. 

A third group of ion-exchange supports are pellicular, consisting of a solid inert core made of PSDVB agglomerated with 350 nm functionalized latex. The quaternary amine groups are closely and uniformly bound on the microbeads, improving flow and reducing nonspecific retention. These pellicular supports are primarily used for carbohydrate analysis [7]. 

Chemically bonded octadecyl groups on a pellicular support was used as stationary phase for the separation of a series of Mitragyna oxindole alkaloids4 with methanol - water (4 1) as mobile phase. 

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