Ruthenium(II) tris(bipyridyl) ion as a luminescent probe for oxygen uptake on the catalyzed oxidation of HSO3−

The present work describes an alternative technique for monitoring the rate of oxygen consumption during the oxidation of HSO3− catalyzed by manganese and iron ions. The method is based on the spectrofluorimetric monitoring of the quenching effect of molecular oxygen on the emission of the photoexcited [Ru(bipy)3]2+ ion, added to the reaction mixtures. The effects of Fe(III), at very low concentrations, and of Mn(II) on the oxidation of HSO3− by dissolved oxygen, have been investigated. The metal ions in the trivalent oxidation state react with HSO3− to initiate a radical chain reaction in which HSO3− is oxidized to sulfate and the metal ion is reduced to the divalent state. The synergistic effect of Mn(II) and Fe(III) was clearly evaluated. Possible parallel reactions with the oxygen indicator, [Ru(bipy)3]2+, are considered.