Abstract
A sensitive and accurate UV-assay procedure based on multiple linear regression analysis (MLR method) was developed for the measurement of uric acid with uricase. The absorbance at 290 nm of uric acid as a function of time was calculated from the color points of a mixture of uric acid, an intermediate (1-carboxy-2, 4, 6, 8-tetraazabicyclo [3.3.0] octa-4-ene-3, 7-dione) and the final product (allantoin) by the simplified complementary tristimulus colorimetry (SCTS method). The MLR method allowed the evaluation of both initial and final absorbances at the same wavelength with high accuracy. The average recovery of uric acid added to an aqueous solution was 99.9±0.02%, and the coefficient of variation was less than 3% (n=4) even at low concentration. The assay could also be performed directly on serum samples without deproteinization. An average recovery of 103.1±0.7% was obtained for 0.17-1.33 mg/dl of uric acid in serum solutions, and the coefficients of variation of 0.32 mg/dl and 0.41 mg/dl were 1.6% (n=4) and 2.4% (n=4), respectively.
