Aqueous systems advantages

The preparation of molecular composites by electropolymeriza tion of heterocycles in solution with polyelectrolytes is an extremely versatile technique, and many polyelectrolyte systems have been studied. The advantages of this method include the use of aqueous systems for the polymerization. Also, the physical and mechanical properties of the overall composite depend on the properties of the polyelectrolyte, so material tailorabiUty is feasible by selection of a polyelectrolyte with desirable properties. 

In order to broaden the field of biocatalysis in ionic liquids, other enzyme classes have also been screened. Of special interest are oxidoreductases for the enan-tioselective reduction of prochiral ketones [40]. Formate dehydrogenase from Candida boidinii was found to be stable and active in mixtures of [MMIM][MeS04] with buffer (Entry 12) [41]. So far, however, we have not been able to find an alcohol dehydrogenase that is active in the presence of ionic liquids in order to make use of another advantage of ionic liquids that they increase the solubility of hydrophobic compounds in aqueous systems. On addition of 40 % v/v of [MMIM][MeS04] to water, for example, the solubility of acetophenone is increased from 20 mmol to 200 mmol L ... 

Reticulated Bacterial Cellulose. A cellulose with an intertwined reticulated structure, produced from bacteria, has unique properties and functionalities unlike other conventional celluloses. When added to aqueous systems, reticulated bacterial cellulose improves the fluid rheology and the particle suspension over a wide range of conditions [1836]. Test results showed advantages in fluid performance and significant economic benefits by the addition of reticulated bacterial cellulose. 

Sample preparation techniques vary depending on the analyte and the matrix. An advantage of immunoassays is that less sample preparation is often needed prior to analysis. Because the ELISA is conducted in an aqueous system, aqueous samples such as groundwater may be analyzed directly in the immunoassay or following dilution in a buffer solution. For soil, plant material or complex water samples (e.g., sewage effluent), the analyte must be extracted from the matrix. The extraction method must meet performance criteria such as recovery, reproducibility and ruggedness, and ultimately the analyte must be in a solution that is aqueous or in a water-miscible solvent. For chemical analytes such as pesticides, a simple extraction with methanol may be suitable. At the other extreme, multiple extractions, column cleanup and finally solvent exchange may be necessary to extract the analyte into a solution that is free of matrix interference. 

There are many advantages of two-phase systems over aqueous systems when they are used as biocatalysis media [21,22,26,27] components (substrates and/or products) can be... 

In studying the stability of colloidal dispersions it is of considerable advantage if the particles concerned are monodisperse and spherical. For aqueous, charge-stabilised systems polymer latices have proved invaluable in this regard. With non-aqueous systems, steric stabilisation is usually required. In this case it... 

New possibilities exist for the development of piezoelectric devices using so-called 1-3 composites. These consist of an array of piezoelectric pillars embedded in a pliable material providing a transducer in the form of a flexible sheet (Fig. 7.5) which can be moulded to fit the shape of a reactor. A particular advantage of such a system is that the emitting face is a combination of ceramic and plastic and can provide much better acoustic transmission into aqueous systems. 

The choice of base used in the Ter Meer reaction is important for two reasons. First, studies have found that strong bases, such as alkali metal hydroxides, inhibit the reaction and promote side-reactions, whereas the weaker alkali metal carbonates generally give higher yields.Secondly, if the m-nitronitronate salt needs to be purified by filtration it should be sparingly soluble in the reaction solvent and both the reaction solvent and the counterion of the gm-nitronitronate salt affect this solubility. Use of the potassium salt is advantageous for aqueous systems where the em-nitronitronate salts are usually only sparingly soluble, whereas the sodium salt can be used for nonaqueous reactions. 

The application of SCF as reaction media for enzymatic synthesis has several advantages, such as the higher initial reaction rates, higher conversion, possible separation of products from unreacted substrates, over solvent-free, or solvent systems (where either water or organic solvents are used). Owing to the lower mass-transfer limitations and mild (temperature) reaction conditions, at first the reactions which were performed in non-aqueous systems will be transposed to supercritical media. An additional benefit of using SCFs as... 

Fn/ymes display a number of characteristic features 17 They catalyze cnanlioselective reactions, are usually substrate specific, usually display their gieatest catalytic activity in aqueous systems, and are generated in nature in only one asymmetric form. The greatest advantage of enzyme-catalyzed asymmetric synthesis is that the availability of the correct enzyme makes it possible to prepare large amounts of an enantiomericaJly pure compound with relatively little effort... 

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