[Determination of oxalic acid by high performance liquid chromatography]

In order to determine a reliable method for measuring oxalic acid, we carried out a procedure using high performance liquid chromatography. This method proved to be excellent in the case of tea and beer. In the case of urine, however, it had some problem from the aspect of reproducibility, although as far as linearity measurement, dilution test and recovery rate were concerned, accurate results could be obtained. Nevertheless, this method was thought to be unsuitable for routine clinical use, at least at present, for the reasons that it took a long time to perform the measurement, and because of the high cost of the column used in the procedure. The value of the oxalic acid as determined by this method in 24 hr urine from 12 healthy male volunteers was in the range of 17-47 mg/day (average +/- standard deviation: 25.4 +/- 9.0). To correct for their differences of physical constitution, dividing oxalic acid value by body weight rather than by urinary creatinine or body surface area was found to give a more precise value of the norm. From this calculation, it was thought that the normal range of oxalic acid value was 0.6 mg/kg or less.