Analysis on Heat Coagulated Blood and Serum. Iv. Direct Determination of Uric Acid by Ultraviolet Absorption.

A direct ultraviolet absorption method that does not require uricase for the determination of serum urate is presented. Serum (0.3 ml.) is placed in the bottom of a 25 X 95-mm. shell vial and coagulated by immersion of the vial in boiling water for 2 mm. The clot is overlaid with 3.0 ml. of water and the serum urate extracted for 60 mm. at 37#{176}. The absorbance of the extract is measured at 295 m, and the serum urate determined by comparison with the known absorption of pure urate at the same wavelength. The agreement between the direct ultraviolet method and a standard phosphotungstate reduction method is excellent in cases in which no medication is being administered. Some drugs absorb ultraviolet light, and in certain instances may be responsible for a discrepancy up to 1.5 mg./100 ml. between the two procedures. The method is extremely simple and requires no reagents.