Methods for determination of urea in human samples can be devided into three diferent groups – biosensors, methods with spectrometrical detection and flow-based methods. Most of them use enzyme urease, which catalyzes reaction of hydrolysis of urea. Products of this reaction are ammonia and carbon dioxide. Even though hydrolysis is the first step for determination of urea, most methods for determination of urea use one or both products of catalyzed reaction of hydrolysis of urea or they detect change of pH in a sample solution. The important parameters in selection of a method for determination of urea are: coefficient of determination (R2), linear range of concentration, limit of detection, stability, duration of analysis and selectivity. After a comparison between the described methods, the more promising ones for determination of urea are: optical biosensors based on polyaniline thin films, electrochemical determination of urea using a gold nanoparticle-copolymer, a paper-based device for the colorimetric determination of urea using silver nanoparticles and automated spectrometric determination of urea by gas-segmented continous flow analysis.
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