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The paper describes the development of electrochemical methods for analytical determination of uric acid basing on amperometric sensors: with an uricase enzyme electrode, termed "electrochemical-enzymatic" method; with an enzyme-free electrode by indication of the anodic oxidation of uric acid, termed "electrochemical" method. The comparison of analytical quality of both methods shows a sufficient specificity, precision, and accuracy. They show a good correlation with regard to the specific uricase-catalase reference method (UCM): yelectr./enz. = (0.943 xUCM + 19.8) mu mol/l; r = 0.9948 yelectr. = (0.964 xUCM + 6.31) mu mol/l; r = 0.9917 The analysis by the "electrochemical" method can be done with a higher frequency of samples per hour completely without need of enzyme. Both methods are principally suitable for an application in analytic biochemical laboratories.

The construction and operation of a measuring device containing an enzyme electrode is described. Glucose oxidase is enclosed in an acrylamide film by means of photopolymerization. The maximal increase of the anodic current of the H2O2 being formed in the enzyme reaction serves as measuring signal. The device gives for diluted serum and blood correlation coefficients above 0,99 according to the methods given in the German Pharmacopeia 7. The measuring time for each specimen is roughly 90 s, the serial variation coefficient 2%.

The peroxidase activity of deuterohemin and deuterohemin complexes relative to the substrates pyrogallol and ascorbic acid was studied using d.c. polarography in aqueous solution. Imidazole and pyridine served as complex ligands. In the absence of the ligands, a continual rise in the substrate conversion rate with increasing H2O2 initial concentration is observed. Imidazole or pyridine were found to considerably increase the peroxidase activity of deuterohemin at low H2O2 concentrations. At high H2O2 concentrations, the dependence of the reaction rate on H2O2 concentration shows a bend, the reaction rate being in each case higher than that of free hemin under the same conditions. The reason of this fact is discussed to be a retarded formation of activated H2O2 hemin-ligand complexes at high H2O2 concentrations.