Spectrophotometric determination of microamounts of ruthenium using 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminoaniline

A new spectrophotometric method for determination of ruthenium with 2 (3,5 dichloro 2 pyridylazo) 5 dimethylaminoaniline(3,5 diCl PADMA) was reported. In the medium of HAc NaAc buffer solution(pH 4.0～6 0),Ru(Ⅱ) could react with 3,5 diCl PADMA to form a stable complex in boiling water bath. The complex could be changed into another stable green blue species of higher sensitivity by addition of mineral acid, e.g, HCl,H 2SO 4 et al . The apparent absorptivity is 1 07×10 5 L·mol -1 ·cm -1 at 636 nm. Beer's law is obeyed in the range of 0～0 9 mg/L for Ru(Ⅱ). Most common ions did not interfere the determination of Ru(Ⅱ) with the masking reagent of EDTA. The method was applied to the determination of trace amounts of ruthenium in samples with satisfactory results.