Comparison of the Archibald-Kern and Stransky colorimetric procedure and the Praetorius enzymatic procedure for the determination of uric acid.

HE ESTABLISHMENT AND ACCEPTANCE of an analytic procedure as a method to be relied upon with complete confidence demands: (1) 8pecific’tty of the method, i.e. minimal interference by other compounds; (2) quantitative recovery of the specific substance when it is added to the medium in which it is usually determined; and (3) reproducibility of results within reasonable limits on replicate samples. The colorimetric methods for the determination of uric acid depend upon the mild oxidation of uric acid in an alkaline or acid medium by molybdate-free phosphotungstic acid (1, 2), arsenotungstic acid (3, 4), or ferricyanide (5, 6, 7). The latter method has been used in combination with the specific enzyme uricase. Among the sources of error associated with these procedures are the inhibition of the uric acid reaction by some of the blood constituents and the precipitation of uric acid with the serum protein in the preparation of a protein-free filtrate, which would yield results below those obtained by uricase. The presence of other substances in blood filtrates which may also reduce the nonspecific oxidizing agents