SPECTROPHOTOMETRIC DETERMINATION OF URIC- ACID IN SERUM USING A TITANIUM(IV)-PORPHYRIN COMPLEX

Aqueous solution of o[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium (IV) complex, a Ti-TPyP reagent, was found to be very useful for the spectrophotometric determination of hydrogen peroxide. The reagent (la mbda(max) 432 nm) reacts with hydrogen peroxide to form a monoperoxoco mplex, resulting in a significant decrease of the absorbance at 432 nm . The decrease (DELTAA) in absorbance was proportional to the concentr ation or hydrogen peroxide. The Ti-TPyP reagent was successfully appli ed to the assay of uric acid in the serum, using uricase to produce hy drogen peroxide through enzymatic oxidation. Using only 5 mul serum, a linear relationship was obtained between DELTAA and uric acid concent ration in the serum ranging from 5 x 10(-6) to 1 x 10(-3) M. The appar ent molar DELTAA of uric acid was 2.2 x 10(5) m-1 cm-1. The relative s tandard deviation of repeated runs (n=8) was 2.8% at 3.77 x 10(-4) m u ric acid. The analytical recovery of uric acid (5 x 10(-4) M) added to the serum was 96.8 to 105.0%. No pre-concentration and deproteinizati on were required to determine uric acid in the serum by the present me thod because of the high sensitivity and selectivity of the Ti-TPyP re agent for hydrogen peroxide.