OXO[5,10,15,20-TETRA(4-PYRIDYL)PORPHYRINATO]TITANIUM(IV) - AN ULTRA-HIGH SENSITIVITY SPECTROPHOTOMETRIC REAGENT FOR HYDROGEN-PEROXIDE

The water-soluble titanium(IV)-porphyrin complex, oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) [TiO(tpypH4)4+], was found to enhance the spectrophotometric determination of trace amounts of hydrogen peroxide. A 0.05 mol dm-3 hydrochloric acid solution containing TiO(tpypH4)4+ was used (the Ti-TPyP reagent), the absorbance of which decreased at 432 nm as hydrogen peroxide was added. This was due to the consumption of the TiO(tpypH4)4+ complex following the formation of peroxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV). The decrease in absorbance at 432 nm (DELTAA432) was proportional to the concentration of hydrogen peroxide, from 1.0 x 10(-8) to 2.8 x 10(-6) Mol dm-3, in the sample solution (25 pmol-7.0 nmol per assay). The reaction was accelerated by hydrogen ions; the presence of 1.6 mol dm-3 perchloric acid was found to promote complexation to the greatest extent. A DELTAA432 Of 1.9 x 10(5) was found for 1 mol dm-3 hydrogen peroxide. A measurement precision of 1.2% for 1.0 x 10(-6) mol dm-3 hydrogen peroxide (n = 8) was obtained. The reagent can be used for the determination of hydrogen peroxide in water samples such as tap water and rainwater over the range from 1.05 x 10(-7) to 3.34 x 10(-5) mol dm-3.