Different combinations of metallic nitrates and bromides were used as redox mediators in the conversion of sulfides to sulfoxides. The metal salts were used in catalytic amounts in the oxidation reaction. It is suggested that in the oxidation and oxygenation processes are involved species originated from the nitrate/nitrite redox cycles and/or the dissolved atmospheric dioxygen and/or coordinated water molecules, all in combination with the redox couple 2Br(-) reversible arrow Br-2 + 2e(-). The utilized metallic centers showed distinct reactivity; Fe-III appears as the best metallic center. (C) 2003 Elsevier Science B.V. All rights reserved.