Colorimetric determination of urinary oxalate recovered as calcium oxalate. Application of a simple correction factor for incomplete preciptation.

A method is described for determination of oxalate in urine. Prior to the determination the oxalate is first precipitated from the urine as calcium oxalate. Correction for incomplete precipitation can be made by applying one simple correction formula. The extent of this correction has been established by determination of the recovery of added [14-C] oxalate. The determination of the precipitated oxalate was carried out by an automated version of the colorimetric reaction of oxalate with uranium and 4-(2-pyridylazo)-resorcinol as originally described by Neas, R.E. and Guyon, J.C. in 1972 (Anal. Chem. 44, 799-805).