FIA of urine oxalate by the titanium(IV)-4-(2'-pyridylazo)resorcinol reagent

A sensitive and selective FIA using the Ti-PAR {4-(2-pyridylazo)resorcinol} reagent was developed for the determination of oxalate in urine. Flow injection manifold was composed of a three-channel system with immobilized oxalate oxidase and ion-exchange columns. All of the solution were pumped at a flow rate of 0.3 ml/min. The sample solution (5 μl) was injected into a sample carrier stream and passed through the oxalate oxidase column, which converted the oxalate to hydrogen peroxide. The produced hydrogen peroxide was then monitored by measuring the absorbance (508 nm) of the Ti(IV)-PAR-H2O2 complex formed with the Ti-PAR reagent. The results were not affected by the presence of metallic ions, such as Fe3+and Ca2+and reducible substances in urine. The responses were linear between 2×10-6 and 1×10-3M oxalate, and the relative standard deviation was1.0% (n=10) at4×10-5 M (200pmol/injection). The throughput rate was 40 samples/h.