Effect of Cobalt(II) and Manganese(II) on the Chemiluminescent Reaction of Peroxymonosulfate with Humic Acid and Some Organic Compounds. Analytical Applications

Abstract

The intensity of the radiation emitted by humic acid (HA) in the presence of SO₅ ²⁻ in basic medium was used to determine HA in the range up to 20.0 mg l⁻¹. The detection limit was 0.24 mg l⁻¹. The addition to the sample of 50 mg l⁻¹ of Co(II) or Mn(II), as EDTA complexes or chloride salts, enhanced the radiation emission as a result of the formation of strong oxidant radicals such as SO₅ ^•−, SO₄ ^•−, and HO^•. In the presence of these metal ions, the oxidation of HA and the catalytic decomposition of SO₅ ²⁻ occur simultaneously. Low concentration of HA in natural waters can be detected. HA was replaced by some model organic compounds. The marked chemiluminescent (CL) signals followed the order: phloroglucinol>fulvic acid>humic acid>resorcinol>pyrogallol>cathecol>hydroquinone.

Keywords:

• Chemiluminescence
• peroxymonosulfate
• humic acid
• cobalt
• manganese
• polyphenols

This work was supported by FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) and CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico). Thanks to Professors Julio C. Rocha, Jorge C. Masini and Maria O. de Oliveira Rezende for providing the samples used in this work.