Carrier material

In appUcations in which electrical conductivity is required, metals, copper, tungsten, molybdenum, and Kovar [12606-16-5] are the preferred chip-carrier materials. Metals have exceUent thermal conductivities. Tables 2 and 3 Ust the various materials used for substrates, along with their mechanical, electrical, and thermal properties. 

When the reaction product is soluble in water, enzyme regeneration is difficult to achieve, since the enzyme is often lost during isolation of the product. One way to overcome this problem is application of immobilised enzyme systems. The enzyme is either covalently or ionically attached to an insoluble carrier material or is entrapped in a gel. Depending on the size of the particles used, a simple filtration and washing procedure can be used to separate the immobilised enzyme from the dissolved product A well-known example of this technique is the industrial production of 6-APA. 

Here we will focus on the biochemical aspects. The techniques of isolating enzymes, the process of enzyme immobilisation and the behaviour of immobilised enzyme reactors are discussed in detail in the BIOTOL text Technological Applications of Biocatalysts", so will not deal with these aspects in detail here. In outline, however, once the desired enzyme is isolated, it is attached to a carrier material. In order to ascertain sufficient accessibility of the enzyme, a bifunctional spacer molecule is attached to the carrier ... 

Off-resin analysis is analysis of a compound cleaved off a polymeric carrier material, usually in solution. 

Like enzymes, whole cells are sometime immobilized by attachment to a surface or by entrapment within a carrier material. One motivation for this is similar to the motivation for using biomass recycle in a continuous process. The cells are grown under optimal conditions for cell growth but are used at conditions optimized for transformation of substrate. A great variety of reactor types have been proposed including packed beds, fluidized and spouted beds, and air-lift reactors. A semicommercial process for beer used an air-lift reactor to achieve reaction times of 1 day compared with 5-7 days for the normal batch process. Unfortunately, the beer suffered from a mismatched flavour profile that was attributed to mass transfer limitations. 

Heating in an autoclave only Steam-sensitive chemical Usually an organic chemical in a printing ink base impregnated into a carrier material. A combination of moisture and heat produces a darkening of the ink, e.g. autoclave tape. Devices of this sort can be used within dressings packs to confirm adequate removal of air and penetration of saturated steam (Bewie-Dick test) Saturated steam... 

Polymer rod carrier material Porous glass Polymer type Polystyrene- divinylbenzene... 

Aluminas. Aluminas, porous AI2O3, are available in many forms. They constitute the most important carrier material in heterogeneous catalysis. Alumina is amphoteric and, as a con.sequence, soluble in both acidic and basic media. Precipitation can be performed from an acid solution by adding a base or from a basic solution by adding an acid, as schematically represented in Fig. 3.18. If, for example, at a pH of less than about 3 a base is added to an aqueous solution of aluminium sulphate, a precipitate is formed. If this material is filtered, dried and calcined, an amorphous porous AI2O3 is obtained. At other pH values different porous aluminas can be synthesized. 

Activated carbons. Activated carbons are high-surface-area carbons. They are extensively used in industry, mainly as adsorbent. They are also used as a carrier material in catalysis because of their rather unique properties ... 

Preparation of such plates requires care and practice, and whereas they were once popular, they have now been replaced by commercial plates for most, if not all, applications. The quality of the commercial plates is good, and they have the added advantage of tolerating handling, which is often a problem in the case of homemade plates in which the layers are readily damaged. The phases are attached to the surface of the carrier material, glass, plastic, or metal by means of binders that do not affect separation but stabilize the mechanical properties of the layers in commercial plates. 

The emission spectmm of Co, as recorded with an ideal detector with energy-independent efficiency and constant resolution (line width), is shown in Fig. 3.6b. In addition to the expected three y-lines of Fe at 14.4, 122, and 136 keV, there is also a strong X-ray line at 6.4 keV. This is due to an after-effect of K-capture, arising from electron-hole recombination in the K-shell of the atom. The spontaneous transition of an L-electron filling up the hole in the K-shell yields Fe-X X-radiation. However, in a practical Mossbauer experiment, this and other soft X-rays rarely reach the y-detector because of the strong mass absorption in the Mossbauer sample. On the other hand, the sample itself may also emit substantial X-ray fluorescence (XRF) radiation, resulting from photo absorption of y-rays (not shown here). Another X-ray line is expected to appear in the y-spectrum due to XRF of the carrier material of the source. For rhodium metal, which is commonly used as the source matrix for Co, the corresponding line is found at 22 keV. 

The TLC process is an off-line process. A number of samples are chromatographed simultaneously, side-by-side. HPTLC is fast (5 min), allows simultaneous separation and can be carried out with the same carrier materials as HPLC. Silica gel and chemically bonded silica gel sorbents are used predominantly in HPTLC other stationary phases are cellulose-based [393]. Separation mechanisms are either NPC (normal-phase chromatography), RPC (reversed-phase chromatography) or IEC (ion-exchange chromatography). RPC on hydrophobic layers is not as widely used in TLC as it is in column chromatography. The resolution capabilities of TLC using silica gel absorbent as compared to C S reversed-phase absorbent have been compared for 18 commercially available plasticisers, and 52 amine and 36 phenolic AOs [394]. 

Other noteworthy developments are carrier materials, such as Stamypor (DSM) and Accurel (AKZO), for production of concentrates with liquid or low-melting additives and reactants (see Section 1.2.1). The biggest growth area for additive carriers is coming from liquid peroxides and silanes, due to related health and safety issues for shopfloor staff. The NOR HALS stabiliser Tinuvin 123-S (a non-interacting, low-MW liquid) for TPO, PP and some blends is delivered in a solid carrier (Accurel). 

M Westerberg, C Nystrom. Physicochemical aspects of drug release. XVII. The effect of drug surface area coverage to carrier materials on drug dissolution from ordered mixtures. Int J Pharm 90 1-17, 1993. 

It is very seldom that a commercial catalyst consists of only a single chemical compound or element. Often the active constituent is supported on a carrier material that may or may not possess catalytic activity of its own. Enhanced catalytic activity, selectivity, or stability may also be achieved by the addition of other materials referred to as promoters or inhibitors. 

Ying, Z.-S. Gevert, B. Otterstedt, J.-E., and Sterte, J., Hydrodemetalation of residual oil with catalysts using fibrillar alumina as carrier material. Applied Catalysis, A General, 1997. 153(1-2) pp. 69-82. 

The decolorization of Reactive Red 2 (azo dye) and Reactive Blue 4 by immobilized fungus Bjerkandera sp. strain BOL 13 was studied [56]. Birch wood was used as a carrier material and circular disks were used in the continuous rotating biological contactor. The experiment results showed the fungus to be able to decolorize mixtures of both dyes efficiently. Decolorization was found to be approximately same at 50 and 100 mg/L of dye stuff (96 and 94%, respectively). When the concentration was increased to 200 mg/L, decolorization decreased to 81%. 

Zhanyuan, L., Zhizhong, C, Binbin, S. 2005. The processed of the carrier material in the cathode receiver. Geophysical Geochemical Exploration, 5 (in Chinese). ... 

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