Cellulose copolymer textiles are modified by plasma irradiation treatment to graft ionic groups onto the fiber. The number of ionic groups are deduced from the ion-exchange capacity of the textile, as measured by determining of the amount of fixed ions on the textile (Yakup Arica 2000). The experimental procedure will now be described.
For anion-exchange textiles, the tissues are equilibrated in sodium chloride solution (1 M) for 24 h. Solutions are changed three times (the corresponding total volume is 500 ml/cm2 of textile). The textiles are then rinsed with demineralized water and dried at 50 °C overnight. Then they are immersed in nitric acid solution (0.1 M) for 24 h to exchange chloride ions with nitrate ions. The concentration of chloride ions is determined by titration with silver nitrate. The final titration point is determined by potentiometric measurement.
Cation-exchange textiles are equilibrated in sodium hydroxide solution (1 M) for 24 h. After rinsing with demineralized water and drying at 50 °C overnight, the textiles are immersed for 24 h in HCl solution (0.1 M) to exchange sodium ions with protons. Sodium ion concentration is then analyzed by photometric measurement.
The exchange capacity (EC) is calculated as the ratio of co-ion in solution per unit of weight of dry textile.
C being the co-ion concentration, V the volume of the solution, and M the mass of dry textile.
A biotinylated enzyme is prepared by adding a fixed amount (2 mg/ml) of enzyme solution, either urease, uricase, or xanthine oxidase), in 100 mM phosphate buffer, pH 7.5, to 100 times mole excess ofbiotin-amidocaproate N-hydroxysuccinimide ester. The biotinylated reaction is carried out at room temperature in a vial with constant stirring for 3 h. After this, 10 mg of glycine is added to react with the unused biotin. Removal of all small-molecular-weight reactants and products is achieved by chromatography through a Sephadex G 25 column from SIGMA (USA) (with a cut-off at molecular weight 25,000).
The biotin-modified textile support is rinsed with distilled water and immersed in 2 ml of an aqueous solution of avidin (1mg/ml) for 1 h. The resulting porous material is washed with distilled water and immersed in a solution of 2 ml biotinylated enzyme (2 mg/ml) for 1 h and then washed again with distilled water.
The modified textile is tightly packed (0.5 cm in thickness) into a glass column of 1 cm in diameter, 10 cm high for chromatography. The column is filled with the studied solution at the top of the column, and this solution flows through by gravity or is circulated by pumping with a peristaltic pump (flow rate: 2 ml/min) and is analyzed at its exit
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