Determination of uric acid in human urine by capillary zone electrophoresis with indirect laser-induced fluorescence detection.

A CZE with indirect LIF detection method was used for the determination of uric acid (UA) in human urine. UA and its coexisting analytes (i.e. hypoxanthine, xanthine and ascorbic acid) could be well separated within 4.5 min at a voltage of 25 kV with 25°C cartridge temperature in a running buffer composed of 5 mM sodium borate, 10% methanol (v/v) and 0.3 μM fluorescein sodium (apparent pH of the final mixed hydro-organic solution of sodium borate, methanol and fluorescein is 9.5). Under the optimum condition, the method has good linearity relationships (correlation coefficients: 0.9973-0.9987) with ranges of 25-500, 25-350, 25-250 and 25-300 μg/mL for hypoxanthine, ascorbic acid, xanthine and UA, respectively. The detection limits for the analytes were in the range of 0.29-0.90 μg/mL. The intra-day RSD values for migration times and peak areas were less than 0.43 and 3.27%, respectively. This method was applied to the quantitation of UA in human urine with recoveries in the range of 93.1-107.3%.