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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.
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.
