CONDITIONS AFFECTING THE COLORIMETRY OF OROTIC-ACID AND OROTIDINE IN URINE

Abstract

Conditions affecting a colorimetric assay of total orotic acid (orotic acid plus orotidine) in urine are studied. Most interfering substances can be conveniently removed on a small column of cation-exchange resin, and an improved control reaction corrects for residual background color. Analytical recovery from urine is nearly complete (> 95%) and the absorption spectrum for analyte eluted from the column closely resembles that for an orotic acid standard. Reference intervals are determined for total orotic acid, expressed as a molar ratio to creatinine, for neonates, children and adults, and assessed the effect of age, protein intake and pregnancy. The method is simple enough to use as a reliable and accurate urine-screening test for metabolic diseases.