Resin bead

Two classes of micron-sized stationary phases have been encountered in this section silica particles and cross-linked polymer resin beads. Both materials are porous, with pore sizes ranging from approximately 50 to 4000 A for silica particles and from 50 to 1,000,000 A for divinylbenzene cross-linked polystyrene resins. In size-exclusion chromatography, also called molecular-exclusion or gel-permeation chromatography, separation is based on the solute s ability to enter into the pores of the column packing. Smaller solutes spend proportionally more time within the pores and, consequently, take longer to elute from the column. 

Steam-Chest Expansion. In steam-chest expansion the resin beads in which gas is already present are poured into molds into which steam is injected. The steam increases the temperature close to the melting point and expands within the stmcture to create beads with food cushioning and insulating properties. Expanded polystyrene is widely used in this process for thermal insulation of frozen food packaging. 

The numerical results for the case of two counterions of equal valence where a resin bead, initially partially saturated with A, is completely converted to the B form, is expressed by ... 

Resistance to Fracture - The ion or ionized complexes that the resins are required to fix are of varied dimensions and weights. The swelling and contraction of the resin bead that this causes must obviously not cause the grains to burst. 

Iron fouling is caused by both forms of iron ions the insoluble form will coat the resin bead surface and the soluble form can exchange and attach to exchange sites on the resin bead. These exchanged ions can be oxidized by subsequent cycles and precipitate ferric oxide within the bead interior. 

The base exchange process removes both the temporary and permanent hardness salts from the water by allowing the water to flow through resin beads containing sodium zeolite, Na2Z. 

Organic trap designs are available that employ a combination of activated carbon and cross-lined resin beads without ionic functionality. 

Resin bead polymer composition Either acrylic resins or, more generally, styrene (vinylbenzene, VB) are cross-linked with typically 4 to 20% divinylbenzene (DVB) in a copolymer network or matrix. 

Exchange of ionizable materials, primarily dissolved iron. Here the preferred media/process is resin bead deep-bed polishers. Resins may be operated in different cycle modes and where, for example ammonia, morpholine, or AVT programs are employed, specific operating conditions are necessary to avoid adverse effects of the ammonia anion cycle. 

In perhaps more than 70% of cases, the major problem is the physical removal of particulate matter, but also in more than 70% of cases, the polishers selected utilize resin bead deep-bed polishers, which are not necessarily the optimum solution. 

Mixtures containing polystyrene resins should either be shaken or stirred with a mechanical stirrer. Stirring with a magnetic stir bar results in destruction of resin beads and the resulting debris can clog frits during filtrations. 

The polymeric resin beads fill a need that arises from the instability of silica gel and its products to mobile phases of extreme pH (outside a pH range of about 4.0-7.0) and, consequently, are employed in most ion exchange separations. Organic moieties containing ionic groups can be bonded to silica and produce an effective ion exchange media, but the restrictions of pH on phase stability still apply. It follows that ion exchange bonded phases are less popular than the polymer bead alternatives. 

The column, designated as TSKgel DEAE-NPR a weak anion exchanger, was 3.5 cm long and 4.6 mm in diameter packed with non-porous resin beads 2.5 ji in diameter. Thus, the maximum efficiency available at the optimum mobile phase velocity would be about 7,000 theoretical plates. The sample was a crude hexokinase product and an... 

In homogeneous catalysis, the catalytically active species is dissolved in the reaction medium and is present uniformly throughout the system. However, with resin catalysis, the catalytically active groups are anchored to the matrix and in the solvent-resin system are located at the surface of and within the body of the resin bead only. Ion exchangers are, in fact, particulate active. species and when used as catalysts combine with the physical and mechanical benefits of heterogeneous catalysts (Pitochelli, 1980). 

Hacroreticular resins are prepared by suspension polymerization of, for example, styrene-divinylbenzene copolymers in the presence of a substance which is a good solvent for the sononer but a poor swelling agent for the polymer [178-180]. Each resin bead is formed from many microbeads joined together during the polymerization process to create a network of holes and 7 channels. This results in greater mechanical stability,... 

Diffusion is not straightforward inside the resin phase, and this is due to the restrictive influences of the polymer network and because of the charge distribution connected with the fixed ions of the functional groups. The resin phase is consequently related to a porous solid. The effectual diffusivities of metal ions in the resin phase may differ but are largely less than those in the aqueous phase external to the resin phase. If Fick s law is applied to diffusion in a resin bead of radius, r, it may be represented as... 

A method where phospholipids are entrapped in the pores of resin beads, in the forms of multilamellar vesicles, has been described [313-319,376]. In some ways, the idea is similar to that of IAM chromatography, even though the resin is modified differently. The retention indices correlate very well with the partition coefficients measured in liposome-water systems (described below). 

The novel concept of synthesizing a molecule while attached to a swollen cross-linked resin bead was introduced and demonstrated by R. B. Merrifield with the solid-phase peptide synthesis method about 20 years ago (1,2). The procedure involves the covalent attachment of an amino-acid residue to the polymer bead followed by the addition of subsequent amino-acid units in a stepwise manner under conditions that do not disrupt the attachment to the support. At the completion of the assembly of the peptide, the product is cleaved from the resin and recovered. The macro-scopically insoluble support provides convenient containment of the desired product so that isolation and purification from soluble co-products in the synthesis can be achieved by simple... 

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