title: Effect of tetrasodium EDTA on enzymatic determinations of urinary oxalate.
abstract: We studied the effects of pretreating urine samples with tetrasodium EDTA (TEDTA) before measuring urinary oxalate with an enzymatic kit (Sigma). Mean analytical recovery of added oxalic acid was only 49% (SD +/- 13%) when the assay was performed as recommended by the manufacturer, but treating samples with TEDTA improved recoveries (96 +/- 10%). In 20 unselected 24-h urine samples assayed with and without TEDTA treatment, the mean oxalate concentrations were significantly (P less than 0.001) different: 15.6 +/- 8.7 and 12.2 +/- 7.9 mg/L, respectively. TEDTA-treated urine samples stored for 14 days at -20 degrees C lost 20% of their oxalate concentration. Use of TEDTA simplifies sample preparation by eliminating the alkalinizing step needed to dissolve EDTA or disodium EDTA.
mesh_terms: D004492:Edetic Acid / Q000494:pharmacology*; D006801:Humans; D010070:Oxalates / Q000652:urine*; D019815:Oxalic Acid; D010088:Oxidoreductases; D013048:Specimen Handling; D013997:Time Factors
chemical_list: D010070:Oxalates; D019815:Oxalic Acid; D004492:Edetic Acid; D010088:Oxidoreductases; C020598:oxalate oxidase