A novel urinary oxalate determination method via a catalase model compound with oxalate oxidase

This work describes a novel method of urinary oxalate determination based on a catalase model compound MnL(H₂O)₂(ClO ₄)₂ (L = bis(2-pyridylmethyl)amino)propionic acid). Urinary oxalate is first decomposed by the oxalate oxidase into carbon dioxide and hydrogen peroxide. The later is then disproportionated into water and oxygen by the catalase model compound forming a color compound, which can be spectrophotometrically monitored. The oxalate concentration of the sample is quantified according to the UV-vis absorbance of the formed color compound. This model compound method maintains the specificity and sensitivity of the conventional enzymatic assay. It has several advantages over the traditional enzymatic method, including low cost, simplicity, large linear range, and adjustable assay time. The model compound method showed a very good linearity in the range of 0.002-20 mmol L^-1 oxalate, with a detection limit of 2 μmol L^-1 oxalate. The mean urinary oxalate determined by this method was 28.6 μg mL^-1, standard deviation (SD) was 1.07 μg mL^-1, and variation coefficient (CV) is less than 4%. The results are consistent with that acquired from the enzymatic and HPLC methods. The model compound method also showed that the model compounds of the corresponding enzymes can be an alternative to the enzymes, thus the cost of the methods or assays using the enzymes can be greatly decreased.