Isotachophoresis for the determination of oxalate in unprocessed urine.

The principle of isotachophoresis has been used to develop a simple, specific and sensitive analytical procedure for the determination of oxalate in unprocessed urine. Analytical conditions were optimized. The accuracy and precision of the method were estimated. The specificity was checked with oxalate decarboxylase. Separation of oxalate from a number of organic acids was achieved. The influence of factors such as storage, calcium concentration, pH or ionic strength was examined. The 24-h urine excretion rates for healthy children, healthy adults and for patients with idiopathic stone formation were established. Lower absolute excretion rates were found in children and females. Urinary oxalate/creatinine ratios were higher in children than in adults. The mean oxalate excretion in 24-h urines of adult healthy individuals was 413 +/- 150 mumol per 24 h per 1.73 m2 (range 195-732). The mean oxalate/creatinine ratio was 0.033 +/- 0.011 (range 0.018-0.065).