Lattice-type entrapment

For the lattice-type entrapment method a cross-linked water-insoluble polymer, such as polyvinyl alcohol or polyacrylamide, is used to trap the enzymes. A natural polymer, or starch, could also be used in this technique. 

For the microcapsule-type entrapment method, a semi-permeable polymer membrane is used to surround the enzymes. As with lattice-type entrapment, control of the conditions is very important as they can have a detrimental effect on the preparation of the enzyme microcapsules. There... 

The adsorption of polymers, poly(vinyl pyridine) or poly(acrylonitrile) either to coordinate metal atoms or to adsorb biopolymers has been used to prepare chemically modified electrodes for immobihzation of enzymes either by physical or by chemical adsorption (carrier binding), cross-linking, and entrapping at lattice sites or in microcapsules [43]. A wide application of these types of electrodes has been made for electrochemical reactions of biological interest [44]. 

Crystalline substances often form with water molecules located at specific sites in the crystal lattice, which are held in coordination complexes around lattice cations. This type of water is denoted as water of crystallization and is common for inorganic compounds. For example, nickel sulfate forms a well-defined hexahydrate, where the waters of hydration are bound directly to the Ni(II) ion. Extraneous inclusion of water molecules can occur if a coprecipitated cation carries solvation molecules with it. Water also can be incorporated into random pockets as a result of physical entrapment of the mother liquor. Well-defined multiple hydrate species can also form with organic molecules. For example, raffmose forms a pentahydrate. 

To some extent, all precipitates are eontaminated with materials originating from solution in the mother liquor. The general term co-precipitation may be used to cover the many different types of impurity incorporation that can occur, including the surfaee adsorption and lattice entrapment of foreign ions and solvent molecules, the physieal inelusion of pockets of mother liquor, and so on. 

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