Reagent for Hydrogen Peroxide (H₂O₂) Determination

Hydrogen peroxide is ubiquitous in nature and its effects are widespread. For instance, hydrogen peroxide contributes to the generation of acid rain, which is a current global problem. Many biological systems generate hydrogen peroxide in certain enzymatic oxidations. The biological substances can be determined by measurements of hydrogen peroxide. The accurate and rapid determination of small quantities of hydrogen peroxide is an important analytical tool for providing information in a variety of fields. Most of the present ultramicro analyses of hydrogen peroxide, such as POD method, are based on hydrogen peroxide oxidation reactions. These methods suffer from interferences arising from the presence of reducing substance in the sample. These interferences result in poor sensitivity.
Takamura and Matsubara et al. have developed a new spectrophotometric analysis using a Ti-porphyrin reagent.^1-3) This colorimetric method is based on the formation of a Ti-porphyrin-H₂O₂ complex, which is relatively unaffected by interferences from reducing substances. The molar absorptivity of this complex is 190,000M^-1cm^-1, which is much higher than any other coloring reagents. Therefore, it is possible to measure extremely small concentrations of hydrogen peroxide. The lower limits of detection are 10nM by the batch method or 1pmol per injection by the flow injection analysis method (FIA). This method has also been applied to quantitative determination of biological components. For example, the concentration of Uric acid can be determined through an enzymatic reaction producing hydrogen peroxide which is then captured by the Ti-porphyrin reagent.
Incorporation of FIA methodology generally allows for very rapid and highly sensitive measurements and therefore this methodology offers a major improvement over batch methodology. In conclusion, the combination of Ti-porphyrin-H₂O₂ colorimetry and flow injection analysis has been successfully used in the ultramicro analysis of hydrogen peroxide featuring rapid analysis and high precision.