Urea in biological fluids has been determined by a variety of direct and indirect procedures. Some indirect methods depend on the hydrolysis of urea with the enzyme urease to form ammonia, with subsequent quantitation of the ammonia by nesslerization (1-4). Undesirable features of these indirect methods are the use of relatively unstable reagents and loss of ammonia during the procedure. Direct...

urease was immobilized on platinum electrode both by chemical binding and electropolymerization.the conductometric urea biosensor thus prepared showed a detection limit of 4.9×10-5 m and linear dynamic range from 4.9×10-5 to 5.8×10-3 m for urea concentration when the enzyme is covalently immobilized on pt electrodes. conductometric transducers respond to the changes in ionic strength thereby le...

Most of the methods for the determination of urea in blood involve the use of the enzyme urease to hydrolyze the urea, since this reaction is specific. However, instead of crystalline urease (l), crude jack bean meal extracts are used. These extracts have been found to contain other enzymes besides urease, termed “ammonia-producing” enzymes, and their substrates, which may produce large quantit...

Most of the methods for the determination of urea in blood involve the use of the enzyme urease to hydrolyze the urea, since this reaction is specific. However, instead of crystalline urease (l), crude jack bean meal extracts are used. These extracts have been found to contain other enzymes besides urease, termed “ammonia-producing” enzymes, and their substrates, which may produce large quantit...

In a previous paper,3) a colorimetric method for the determination of urea nitrogen in blood and urine was presented on the basis of a color reaction of urea with diacetyl monoxime (DAM) in phosphoric acid solution in the presence of D-glucuronolactone (GL), which served to produce a photo-stable color and eliminate the sigmoidal nature of calibration curve observed usually in the DAM method.4)...

A rapid, relatively sensitive, and low-cost method for the determination of water-soluble urea content in dermatological therapy products and cosmetics is proposed using a new spectrophotometric assay with water as the only extraction solvent. Spectrophotometric methods involve addition of a known excess of bromate to urea in an acid medium, followed by the determination of residual bromine and...

The natural dye hematein in water solution was used as a pH-sensitive redox-active mediator for amperometric pH-sensing. The electrochemical characteristics were studied using cyclic voltammetry and chronoamperometry. Several types of urea biosensors were constructed with urease on the surface of platinum and graphite composite electrodes or in the bulk of the graphite composite. They were used...