Abstract
A rapid and sensitive flow injection analysis (FIA) with spectrophotometric detection by a Ti(IV)-porphyrin reagent is described for the determination of oxalate in foods using an immobilized oxalate oxidase reactor to yield hydrogen peroxide. The reagent is an aqueous solution of oxo[5, 10, 15, 20-tetra(4-pyridyl)porphyrinato]titanium(IV), TiO(tpypH4)4+, which reacts with hydrogen peroxide to form a monoperoxo complex, TiO2(tpypH4)4+, having an absorption peak at 450nm. The absorbance was proportional to the concentration of hydrogen peroxide. The flow-injection manifold comprised a two-channel system with an immobilized oxalate oxidase column. A linear relation was observed between the absorbance and the oxalate concentration ranging from 5×10-7to 2.5×10-4M (r=0.999), and 25 samples could be analyzed in one hour. The relative standard deviation for ten replicate measurements was 0.48% at 2.5×10-5M (500pmol/injection). The application of this system for the determination of oxalate in foods gave satisfactory results. A good correlation (r=0.996) was seen between the results obtained by the proposed method and by the conventional method using a commercial F-kit.
