Modified surface type supports

Although numerous materials have been used for surface functionalization for solid-phase synthesis [15, 31, 32], the most common, which are commercially available, are membranes and pellicular solid supports, where a mobile polymer 

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Several classifications of solid supports have been proposed on the basis of their physical properties [31-32]. However, the solid supports most widely used today can be classified into just two groups gel type and modified surface type. 

POROS media, made by copolymerization of styrene and divinylben-zene, have high mechanical strength and are resistant to many solvents and chemicals. The functional surface chemistry of the particles can be modified to provide supports for many types of chromatography, including ion exchange, hydrophobic interaction, immobilized metal affinity, reversed... 

A typical example of this type of experiments is shown in Fig. 6. Two broad sets of signals are observable which are attributed to the Q - and Tn- groups present at the surface of the silica material SBA-3. The presence of different T -groups confirms not only the successful surface modification but also characterizes the method of attachment of APTES to the silica surface. This example clearly demonstrates that Si CP-MAS is the tool of choice for a detailed characterization of the modified surface of silica support materials. 

Particularly in the beginning of thin-layer chromatography, but also today, sorbents without chemically modified surfaces are of most importance. In former times hand-made thin-layer plates were used nearly exclusively, but today the trend has moved in the direction of industrial precoated layers. In addition to glass plates, plastic and aluminium sheets are also offered as supports for the precoated layers. To stabilize the precoated layers mechanically, special binders are added that do not or nearly do not interfere with the chromatographic properties. To enlarge the possibilities of detection, added indicators can be mixed homogeneously with sorbents. Different types of silica gel are by far the most versatile and therefore the most frequently used stationary phases in the case of bulk sorbents as well as for application to precoated layers. 

Biocatalytic reactions performed using immobilized enzyme microreactors under continuous flow mode have been found effective for hydrolysis reactions [121,158-161], with the enzyme either trapped in the matrix [159], covalently linked to modified surface wall [160,121], enzymes entrapped in hydrogels [162], or enzymes immobilized on monolith [179]. The experimental setup consists of either chip-type microreactors with activated chaimel walls where enzymes bind, enzymes that bind to beads, enzymes entrapped in the matrix, enzymes adsorbed in nanoporous materials, and most recently, nanosprings as supports for immobilized enzymes in chip-based reactors, or enzyme immobilized monolith reactors, where support is packed inside a capillary tube (Table 10.4). 

The mesoporous ordered silicas of different type represent the new generation of materials with unique properties. The discovery of these materials became basis for creation of new catalysts, adsorbents, sensors and supporter for other molecules. The most important way of the modifying physical and chemical properties of mesopurous silicas consist in organic components incorporation on the silica surface as part of the silicate walls or their insertion within channels of the mesopores. This ensured that interest in synthesis and study of functionalized mesoporous materials shai ply grew. In spite of it, these materials are studied insufficiently. 

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