Color reaction of 2-(5-iodine-2-pyridylazo)-5-dimethylaminoaniline with ruthenium(II) and its application

The coloring reaction of 2-(5-iodine-2-pyridylazo)-5-dimethylaminoaniline(5-I-PADMA) with ruthenium(Ⅱ) was studied,and a new spectrophotometric determination method of ruthenium(Ⅱ) was established using 5-I-PADMA as coloring reagent.In HAc-NaAc buffer solution at pH 4.0-6.2,ruthenium(Ⅱ) could react with 5-I-PADMA to form a 1∶2 complex under heating in the presence of NH2OH·HCl.The complex was stable in inorganic acid.The appropriate concentration for HCl,H2SO4,HClO4 and H3PO4 was 0-2.0 mol/L,0-1.8 mol/L,0-1.7 mol/L and 0-3.0 mol/L,respectively.The maximum Absorption wavelength was at 618 nm,and the apparent molar Absorptivity was 5.22 ×104 L·mol-1·cm-1.Beer's law was obeyed for ruthenium(Ⅱ) in the range of 0-1.0 mg/L.Most of the common ions could exist using EDTA as masking reagent.The proposed method has been successfully applied to the determination of trace ruthenium in ruthenium-carbon catalyst and ruthenium-molecular sieve,with relative standard deviations(RSD) of 1.2 % and 0.41 %(n=6),respectively.