Sub-ppm determination of uric acid using a sensitive kinetic-catalytic reaction system

A sensitive and selective kinetic-spectrophotometric method was developed for the determination of trace amounts of uric acid. The method is based on the inhibitory effect of uric acid on the oxidation of Janus Green by bromate in the presence of sulfuric acid. The reaction was followed spectrophotometrically by measuring the absorbance at 518 nm using the fixed-time method. Under optimum experimental conditions (Janus Green, 30.0 μmol L-1; sulfuric acid, 70.0 mmol L-1; bromate, 3.75 mmol L-1; 25 °C and 4.0 min), the calibration curve was linear over the range 0.3 - 46.1 μg mL-1 of uric acid and the detection limit was obtained 0.08 μg mL-1. The relative standard deviations (n=6) of 1.0 and 10.0 mg L-1 of uric acid were 1.14 and 1.08%, respectively. The influence of different foreign species that co-exist with uric acid was investigated in different matrices. The developed method was successfully applied for the determination of uric acid in biological samples.