Measurement of urinary oxalic acid: A comparison of five methods

Objective: Five methods for oxalate analysis in urine are compared with respect to reliability, accuracy, and practicability. Results: Suppressed and unsuppressed ionchromatography, as well as the enzymatic Sigma-Kit, achieve low coefficients of variation for the within-batch imprecision (1.1–8.0%) and between-day imprecision (1.6–7.2%). The results of these methods are comparable and the mean recovery rate ranges between 99.7% and 100.9%. The enzymatic Boehringer-Kit gives higher CV (3.1–9.5%) and the results are lower than those obtained by the methods mentioned above; the recovery rate is sufficient (92.4%). Conclusion: The handling of the chromatographic methods is very easy, whereas the enzymatic methods require more manual work. In relation to sample throughput, changes for the enzymatic methods are about twice as high as for the chromatographic methods. In respect to reliability and accuracy, the chromotropic acid method cannot be recommended (recovery rate 68%).