Membrane chemical compositions, table

Filtration and storage behavior of beer depend strongly on its chemical composition (Table 20.1). Beer production is based on natural ingredients and therefore beer contains a wide variety of chemical compounds. Most chemical components of beer have an influence on beer filtration in general and membrane hltration in particular. Carbohydrates, such as pentosans and (3-glucans, proteins and protein-polyphenol complexes, are of particular importance in membrane hltration of beer, as they are responsible for membrane fouling [3], which has negative consequences on both the hux and quality of the hltered beer, as it will be discussed in detail later on in this chapter. 

Typically, a binary system was selected as the base component of the recipe and the addition of polyelectrolytes to either side (core or receiving bath) was tested to evaluate the change in the capsule properties. The 33 successful multicomponent membrane systems are presented in Table 1. The components of the core material side (21 different chemical compositions) are listed in the first column, while the receiving bath components (20 different chemical compositions) are listed in the second column. With the exception of xanthan and CMC, the first polymer listed on the core side are gelling polymers which form beads with the appropriate ionotropic cation (salt). CMC can also be gelled by ions (alum), although they are considered to be non-compatible for cellular applications. The cations were tested both sequentially, usually with ionotropic cation first, and simultaneously. Walled capsules with adequate mechanical properties were often obtained through the simultaneous application of two polycations. Such a... 

The detailed chemistry of the stratum corneum is complicated by the membrane s composition, formation, and structure. Some gross chemical characterizations have determined the primary chemical components of the tissue which are shown in Table I (29). The tissue is primarily cellular with approximately 10% extracellular components which are lipid and mucopolysaccharides. The bulk of the tissue is densely packed intracellular fibrous protein associated with lipids, resulting in a dry general body corneum density of 1.35-1.40 gm/cm as determined by a gas displacement technique (30). 

The polarization of the electrosorption membranes was carried out at a potential difference of 5 V and 10 V. Electrosorption tests were carried using a simulated solution of an industrial nickel effluent and a mine water source. The chemical composition of both solutions is given in Table 40.3. 

The whey powder (from bovine milk) used in this experiment was purchased from Sigma Chemical Co. (St. Louis, MO, USA). The chemical composition of whey protein is shown in Table 1. Samples were prepared by diluting the appropriate amount of whey powder with water. The concentration of the samples remained at approximately 200,000 ppm. The standard chemicals of a-lactalbumin (Type III deplete, form bovine milk, approximately 85%), p-lactoglobulin (form bovine milk, approximately 90%), and BSA were purchased from Sigma Chemical Co. Standard protein solutions were prepared in water. Standard solutions were made for each protein of 10 mg dissolved in 1 L with water. The water was filtered with HA 0.5-pm membranes (Division... 

Since the ATR-FTIR for the chemical composition analysis is limited to the surface of the membranes, a gel test was carried out on the cross-linked membranes. In this study, the gel contents of the cross-linked membranes were measured by soaking the membranes in THF for 2 days at 25°C. The gel contents increased with the cross-linker concentrations (Table 11.4). This indicates that the degree of cross-linking increased with the cross-linker concentrations, which supports the FTIR results. 

Although a great deal is known about the chemical composition of the mitochondrial membrane and it is established that the membrane contains a number of catalytic proteins e.g., the ATPase synthetase system, an ion transport molecular machinery and electron transport chain), the topological distribution of these proteins in the membrane is not known. All topological models proposed are at present hypothetical [177]. However, it is accepted that the mitochondrial membrane, like most if not all biological membranes, is of the fluid mosaic model and is composed of a lipid bilayer traversed by proteins (see plasma membrane in Chapter 16). Electron microscopic studies of the freeze-edge fractured faces of the outer and the inner membrane [178] indicate that the proteins are asymmetrically distributed not only when the inner is compared to the outer membrane, but also when the inner and outer faces of each of the fractured membranes are compared (Table 1-3). 

Mild homogenization of the bovine retina and centrifugation of the homogenate in a sucrose density gradient permits isolation of an aqueous suspension of photoreceptor membranes (de Grip et al., 1972). The chemical composition of the membrane is presented in Table 1. 

Table 23-2 lists ihe various types of ion-selective membrane electrodes that have been developed. These differ in the physical or chemical composition of the membrane. The general mechanism by which an ion-sclective potential develops in these devices depend.s on the nature of the membrane and is entirely different from the source of potential in metallic indicator electrodes. We have seen that the potential of a metallic electrode arises from the tendency of an oxidation-reduction reaction to occur at an electrode surface. In membrane electrodes, in contrast. Ihe observed potential is a kind of junction potential that develops across a membrane thal separates the anidyte solution from a reference solution. 

To investigate the chemical composition of the membrane surface, XPS analyses of the PSF and PSF-g-AAc membranes were performed and are summarized in Table 7.3. The atomic concentration of S2p for the unmodified PSF membrane is 5.37% and can be used as a reference on the basis that it does not change after UV irradiation. The atomic concentration of grafted membranes, the ratio of to S2P, gradually increases upon prolonging the UV irradiation time up to 150 s (UA5). This indicates that the atomic concentration of Ojs in the surface region increases as AAc is grafted further. 

Weber and coworkers were able to show in an in vitro model, that endotoxin adsorption depends both, on chemical composition and the manufacturing process of the membrane [30], In fact, hydrophobic parts of the lipopolysaccharide molecule (LPS, endotoxin) are considered to interact with hydrophobic entities within the pol-ysulfone structure thereby facilitating their removal [29] (Tables 13.3 and 13.4). 

Table 4.10 Polymer structure, chemical composition and physical properties of TR-polymer and copolymer membranes...

The surface chemical compositions of membranes were determined using ESCA analysis and the results are tabulated in Tables I and II for the SPSF-Na and SPSF-K membranes, respectively. Atomic fractions of C, S, 0, and Na or K for both the top and bottom sides of the membranes are listed in addition to the values of the Na/S and the K/S atomic ratios. Here, the top and bottom sides refer to the side of the dense membrane interfaced with air and glass plate during the casting process, respectively. The precision of the values of the atomic ratios is about 20%. 

Table I. ESCA Analysis of the Surface Chemical Composition of SPSF-Na Membranes.

Typical compositions of polymeric GMs are depicted in Table 26.3. As the table shows, the membranes contain various admixtures such as oils and fillers that are added to aid the manufacturing of the FML but may affect future performance. In addition, many polymer FMLs will cure once installed, and the strength and elongation characteristics of certain FMLs will change with time. It is important therefore to select polymers for FML construction with care. Chemical compatibility, manufacturing considerations, stress-strain characteristics, survivability, and permeability are some of the key issues that must be considered. 

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