Flow-injection Spectrophotometric Determination of Uric Acid in Urine via Prussian Blue Reaction

A simple and sensitive flow injection(FI) spectrophotometric method was reported for the determination of uric acid based on the reduction of Fe(III)/ferricyanide in the presence of uric acid. The in situ reduced ions reacted with unreduced portion of ferricyanide/Fe(III) to form soluble Prussian blue, which was monitored at an absorption wavelength of 735 nm. The optimized conditions allow a linear calibration graph in a concentration range of 1―100 µmol/L. The relative standard deviation was in a range of 0.5%―2.5%, with a detection limit(3σ blank) of 0.3 µmol/L and a sampling frequency of 60 injection/h was obtained. The effect of common substances present in human physio- logical fluids on the determination of uric acid was examined. The method was applied to determining uric acid in human urine samples with the recoveries in a range of 96%―105%. The results agree well with those by spectro- photometric reference method at a confidence level of 95%. Spectrophotometric procedures for uric acid determina- tion in clinical samples were reviewed briefly. Keywords Flow injection analysis; Spectrophotometry; Uric acid; Prussian blue; Urine Article ID 1005-9040(2011)-06-929-05