Sensitive spectrophotometric determination of osmium with pyrocatechol and hydroxyamidine

Abstract

An ethanolic solution of pyrocatechol in the presence of hydroxyamidine and osmium(VIII), on heating at a pH between 7.0 and 9.0, gives a very sensitive colour reaction. The coloured species formed is extracted into dichloromethane and gives molar absorptivities with N¹-hydroxy-N¹,N²-diphenylbenzamidine and its eight derivatives in the range 0.80 × 10⁶–3.45 × 10⁶ dm³ mol^–1 cm^–1 with the wavelengths of maximum absorption at 400–430 nm. The method is extremely sensitive and free from interference from the ions commonly associated with osmium. The method is applicable to the recovery of the metal from ores containing osmium at ppb levels and also from synthetic matrices.