Determination of urinary oxalate by high-performance liquid chromatography monitoring with an ultraviolet detector.

High-performance liquid chromatography (HPLC) monitoring with an ultraviolet detector was carried out to measure urinary oxalate levels in urolithiasis. Interfering substances in urine were removed by anion exchange prior to chromatography. This procedure was found excellent with respect to sensitivity, reproducibility, and analytical recovery. The findings were in agreement with colorimetric date. The mean oxalate level in 24-hour urine was 30.5 +/- 15.1 mg in patients with a single episode and 36.3 +/- 9.8 mg in recurrent stone formers. The latter values was significantly higher than the normal control level (27.4 +/- 3.8 mg).