ENZYME IMMOBILIZATION ON AN EPOXY MATRIX - DETERMINATION OF L-ARGININE BY FLOW-INJECTION TECHNIQUES

A continuous-flow procedure is described for the determination of L-ar ginine, based on its L-arginase catalyzed conversion to L-ornithine an d urea. The urea formed is transformed into ammonia which is measured spectrophotometrically (629 nm) through indophenol blue formation. Arg inase and urea are covalently immobilized on an epoxy resin and are pl aced in a 50 X 3 mm i.d. glass column. This enzyme reactor is stable f or more than 6 months and retains about 80% of its initial activity af ter 800 assays. Under the proposed experimental conditions, concentrat ions of L-arginine > 1.7 mu g ml(-1) (8 mu M) can be determined. The p rocedure has a linear calibration range between 38 mu M and 7.5 mM and a relative standard deviation of 1.8% (12 injections at 50 ppm). Amon g the 22 amino acids investigated, only L-glycine and L-histidine (gre ater than or equal to 960 mu g ml(-1)) interfere.