Catalytic activity of noble metal ions for the degradation of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine in the presence of oxidizing agent, and its application to the determination of ultra trace amounts of ruthenium

Trace quantities of ruthenium(II) ion catalyze the oxidation of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine (TPPS) by potassium bromate. This reaction can be used for the determination of ultra trace amounts of ruthenium using the water-soluble porphyrin with its high molar absorbance. The scope of the reaction was investigated in terms of the reaction conditions and selectivity with respect to other noble metal ions. The effect of pH, concentration of bromate, the reaction time, and the type of metalloporphyrin were studied so as to optimize the method for the determination of trace amounts of Ru(III). The apparent reaction rate constant for the disappearance of TPPS (or metal-TPPS) is proportional to the root of the concentration of bromate, and directly related to that of Ru(III). The limit of detection is 0.11?nM (equal to 10.7?pg?mL^?1) at pH?4.25, where the turnover number is 201. The reproducibility for five measurements at 2.7?nM of Ru(III) was 2.9%.