Inert support materials

The retention mechanism of organic solutes by porous polymer beads remains ambiguous [478]. At low temperatures adso tion dominates but at higher temperatures the polymer beads could behave as a highly extended liquid with solvation interactions. The evidence for a partition mechanism is not very strong and its importance, at present, remains speculative. Like other adsorbents it has proven possible to control retention and enhance efficiency by diluting porous polymers with an inert support material (479). 

Affinity chromatography has become one of the standard techniques for the separation and purification of enzymes. It is based on the idea of utilizing the specific interaction between an enzyme and an immobilized substrate or inhibitor. The substrate is chemically bound to an inert support material, and when a sample is added to the column the enzyme binds to it to an extent depending on the strength of the interaction between the two. Other enzymes and proteins which do not interact with the substrate pass through the system with little or no retention. Removal of the enzyme from the stationary support is accomplished by changing the eluent so as to alter the enzyme-substrate interaction. The... 

The particle sizes for both Pt/SiC>2 catalysts are higher than for the other catalysts. The larger particle size for the Pt/SiC>2 catalysts illustrates that it is very difficult to achieve highly dispersed metal particles on an inert support material. When no interaction between the support and the metal particles is present, the support material loses its primary function to keep the metal particles highly dispersed. 

Electrophoretic Separation. The net charge on a particular protein varies with the pH of the medium in which it is dissolved. Accordingly, application of an electric field to a buffered, heterogeneous protein solution often results in their differential migration in free solution or in heterogeneous systems with an inert supporting material, such as a polyacrylamide gel. Because of the difficulty of scaling up electrophoretic procedures, they are more commonly used for analytical applications than for the preparative scale purification of proteins. The use of electrophoresis is discussed in more detail in Experiment 4. 

Of all the reaction parameters involved in a heterogeneously catalyzed process, the selection of the catalyst is probably the most critical in determining the outcome of a particular reaction. The chapters in this section provide the reader with the information needed to make the selection of the catalyst more efficient. Most of the catalysts used for synthetic reactions are composed of the catalytically active species dispersed on a supposedly inert support material. The nature of the support can influence both catalyst stability and activity. It can also define the procedure best applicable for the preparation of a specific catalyst. Because of this, the commonly used supports are discussed in Chapter 9 to provide the background needed in the discussion of supported catalysts presented in the following chapters. 

A method to circumvent this dilemma was sought by Ferng (11). An extensive and detailed study of static sorption methodology was first conducted to provide a basis of reproducible data for starches of different macromolecular structure. This was followed by studies of sorption isotherms by IGC with different GC conditions including zero loads with empty and supposedly inert support material (diatomaceous earth). The data showed that the response of the thermal conductivity detector (TCD) to controlled chromatographic conditions of temperature, flow rate, and partial water vapor... 

Oxides of a variety of metals on finely divided inert support materials initiate polymerization of ethylene and other vinyl monomers by a mechanism that is assumed to be similar to that of heterogeneous Ziegler-Natta polymerization that is, initiation probably occurs at active sites on the catalyst surface [2j. Unlike the traditional Ziegler-Natta two-component catalyst systems, the supported metal-oxide catalysts are essentially one-component systems. Among the metals that have been investigated for these catalyst... 

The data shown in figure 10.3(C) indicate that the observed signal time course can be altered by varying the RC characteristics of inert support materials. Thus, it appears that the electrical behavior of thin-film devices constructed with electroactive biomaterials may be fundamentally similar to that of conventional microelectronic devices made of inorganic materials. In particular, equivalent-circuit analysis is useful as a design tool in biomolecular electronics. 

It has an NiAs-type structure (Fig. 15-5), and the isolated methyl groups are presumably in the lattice as the pyramidal CHJ ion.35 Sofiium amd potasstuirralkyl5 can be used for metallation reactions- for example, in eq. 6-2. They can also be prepared from Na or K dispersed on an inert support material, and such solids act as carbanionic catalysts for the cyclization, isomerization or polymerization of alkenes. The so-called alfin catalysts for copolymerization of butadiene with styrene or isoprene to give rubbers consist of sodium alkyl (usually allyl) and alkoxide (usually isopropoxide) and NaCl, which are made simultaneously in hydrocarbons.33... 

Besides SPRTs, PRTs are available in many different forms and sizes for a variety of industrial applications [14]. Hie basic design of an industrial PRT involves a length of platinum wire wound on an inert supporting material with proper insulation to prevent shorting. Figure 16.9 shows the construction of some industrial PRTs. 

Another use of vanadium is as a catalyst in a variety of reactions. Vanadium pentoxide, ivhen placed on an inert support material, is the principal catalyst used in the oxidation of SO2 to SO3 in the production of sulfuric acid, and for the conversion of naphthalene into phthalic anhydride during the formation of plastics. In addition, vanadium oxychloride, tetrachloride and triacetylacetonate are used as polymerization catalysts in the production of soluble copolymers of ethylene and propylene. In the reaction vessels, these polymers are viscous liquids, which can trap the vanadium catalysts and result in a vanadium content of up to 500 mgkg in products used for the packaging of food and pharmaceuticals. The disposal of spent catalysts could also be a point source for a contamination of the biosphere and of food with vanadium (Byerrum 1991). Furthermore, vanadium is used for the production of yellow pigments and ceramics. 

Chromatography is a separation technique where component molecules (solutes) in a sample mixture are transported by a mobile phase over a stationary phase. The mobile phase may be a gas or a liquid (solvent system) and the stationary phase may be a liquid film on the surface of an inert support material or a solid surface. The solute, mobile phase and stationary phase form a ternary system. Interaction occurs between the solute and stationary phase so that the solute is distributed between the stationary phase and mobile phase. Attraction of the solute for the stationary phase results in retardation of its movement through the chromatography system. Different components (solutes) will move at differing rates since each will have a slightly different affinity for the stationary phase with respect to the mobile phase. Each component or solute A,B,C) is distributed between the two phases with an equilibrium established defined by the distribution ratio (previously known as the partition ratio) thus for component A... 

Affinity chromatography separation effected by affinity of solute molecules for a bio-specific stationary phase consisting of complex organic molecules bonded to an inert support material, e.g. separation of proteins on a bonded antibody stationary phase. The technique is really selective filtration rather than chromatography. 

Partition chromatography chromatographic separations which involve a liquid stationary phase immobilised on an inert support material. The solutes are distributed between the mobile phase and stationary phases according to their respective partition coefficients. 

Partition coefficient, describes the distribution of a solute between a liquid or gaseous mobile phase and a liquid stationary phase on an inert support material. The solute molecules are partitioned between the two phases according to the retention forces of the stationary phase and the solvating properties of the mobile phase in LC or vapour pressure in GC. The equilibrium is temperature dependent see distribution ratio ... 

Generator Column This method is the same as that used to measure vapor pressure with the exception that water rather than air is passed through the column containing inert support material coated with the compound in question. This procedure avoids the mechanical action that generates the dispersed aggregates, however, if insufficient contact time is provided to establish equilibrium an underestimate of the solubility would result. Solubility data reported for some polynuclear... 

Plant and other lectins have the ability to adhere strongly to microbial cell surfaces and lectins are responsible for the adhesion of Rhizobim trifotii to root hair cells of clover. Discovery of lectins which will bind other microbes may lead to the use of lectins as bridging agents to bind cells to inert support materials. Fletcher (83) studied the effects of proteins on the adhesion of a marine Pseudomonas sp. to polystyrene Petri dishes. Bovine serum albumin, gelatin, fibrinogen and pepsin (pKj — 5.8) all inhibit attachment at pH 7.6 when present either prior to or concurrently with the microbial cells. Bovine serum albumin decreased the adhesion of previously attached cells. 

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