Simple selective spectrophotometric method for the determination of ruthenium in carbon supported Pt-Ru-Ge-catalyst

A simple spectrophotometric method for the determination of ruthenium in the presence of platinum in Pt-Ru-Ge catalyst applied in fuel cells has been developed. Platinum catalyst (20% Pt) with carbon support containing 0.5% Ru and 5% Ge was digested in the mixture of HCl+HNO3 (6+1). Carbon was separated from the examined sample by filtration after dissolution of the metals. Ruthenium was converted into a complex with thiourea (lambda(max)=640 nm, epsilon = 2.9.10(3) 1 mol(-1)cm(-1)) in the medium of 5 M in HCl and 1% in thiourea after 15 min heating at 70 degrees C. Platinum does not interfere with the determination of ruthenium. Germanium is converted into volatile GeCl4 and escapes from the examined sample during the digestion step. The content of ruthenium determined in the examined samples of catalyst amounted to 0.49% (RSD = 0.14%).