Spectrophotometric Determination of Osmium at the PPB Level Using Pyrocatechol and Hydroxyamidine

Abstract

A sensitive method for the spectrophotometric determination of osmium at the ppb level is described. The method is based on the formation of a brown-coloured complex by heating the reaction mixture containing Os(VIII), pyrocatechol and a hydroxyamidine at pH 8.5 over a boiling water bath, with subsequent extraction of the coloured species into chloroform. The molar absorptivity of the coloured species with N-hydroxy-N,N′-diphenylbenzamidine is 3.95 × 10⁶ 1 mol⁻¹ cm⁻¹ at λ_max = 410 nm. The method is free from interferences for almost all ions tested.

Key Words:

• Osmium(VIII)
• extraction
• spectrophotometry
• hydroxyamidine
• low grade ore analysis