Measurement of Urinary Oxalate and Citrate by Capillary Electrophoresis and Indirect Ultraviolet Absorbance

We describe a method for measuring urinary oxalate and citrate with capillary electrophoresis (CE) and indirect ultraviolet absorbance detection. Sample preparation is minimal, requiring an acidification, brief centrifugation, and dilution. The method is rapid, with oxalate and citrate having mean migration times of 4.02 and 4.50 mm, respectively. The minimal detectable concentration (sig-nal-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 concentra-tions of 8-60 mg/L and 80-860 mg/L, respectively. The recovery of added oxalate ranged from 94 % to 101 %. Results of CE analyses agreed well with enzymatic de-terminations of oxalate and citrate. Rapid analysis time, accuracy, and reproducibility make this procedure wel