[Spectrophotometric determination of uric acid in serum using a titanium (IV)-porphyrin complex]

ArticleinYakugaku zasshi journal of the Pharmaceutical Society of Japan 114(1):48-53 · February 1994with5 Reads
Source: PubMed
Abstract
Aqueous solution of oxo[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 (lambda max 432 nm) reacts with hydrogen peroxide to form a monoperoxocomplex, resulting in a significant decrease of the absorbance at 432 nm. The decrease (delta A) in absorbance was proportional to the concentration of hydrogen peroxide. The Ti-TPyP reagent was successfully applied to the assay of uric acid in the serum, using uricase to produce hydrogen peroxide through enzymatic oxidation. Using only 5 microliters serum, a linear relationship was obtained between delta A and uric acid concentration in the serum ranging from 5 x 10(-6) to 1 x 10(-3) M. The apparent molar delta A of uric acid was 2.2 x 10(5) M-1 cm-1. The relative standard deviation of repeated runs (n = 8) was 2.8% at 3.77 x 10(-4) M uric 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 deproteinization were required to determine uric acid in the serum by the present method because of the high sensitivity and selectivity of the Ti-TPyP reagent for hydrogen peroxide.
  • [Show abstract] [Hide abstract] ABSTRACT: Hydrogen Peroxide has been an important analyte in many fields for many years. The Ti-TPyP reagent, i.e., an acidic aqueous solution of oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) complex, was developed as a highly sensitive spectrophotometric reagent for determining traces of hydrogen peroxide. Following the addition of hydrogen peroxide to the reagent, the absorbance at 432 nm decreased and a new peak appeared at 450 nm (the Soret band) accompanied by the consumption of the complex and the formation of its monoperoxo complex, respectively. The degrees of the absorbance changes were found to be proportional to the hydrogen peroxide concentration with the apparent molar absorptivities of 1.9 x 10(5) (432 nm) and 1.1 X 10(5) (450 nm) M-1 cm(-1) (1 M = 1 mol dm(-3)). Both values are much larger than those obtained by the conventional analysis methods. Based on these facts, the determination of hydrogen peroxide was made by a batch method and a flow injection analysis (FIA) method with the detection limits of 25 pmol and 0.5 pmol per test, respectively. In this account, the Ti-TPyP reagent is assessed for determining hydrogen peroxide in rainwater and in the atmosphere, and for determining several components in foods and biofluids mediated by appropriate oxidase enzymes, to demonstrate its potential for a broad range of applications.
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