MEASUREMENT OF URINARY OXALATE AND CITRATE BY CAPILLARY ELECTROPHORESIS AND INDIRECT ULTRAVIOLET ABSORBENCY

We describe a method for measuring urinary oxalate and citrate with ca pillary electrophoresis (CE) and indirect ultraviolet absorbance detec tion. Sample preparation is minimal, requiring an acidification, brief centrifugation, and dilution. The method is rapid, with oxalate and c itrate having mean migration times of 4.02 and 4.50 min, respectively. The minimal detectable concentration (signal-to-noise ratio of 7) of both oxalate and citrate in urine was 7 mg/L. Total imprecisions (CV) were 1.2-5.6% for three urine samples with oxalate and citrate concent rations of 8-60 mg/L and 80-860 mg/L, respectively. The recovery of ad ded oxalate ranged from 94% to 101%. Results of CE analyses agreed wel l with enzymatic determinations of oxalate and citrate. Rapid analysis time, accuracy, and reproducibility make this procedure well suited f or routine urinary oxalate and citrate determinations.