| Revista: | Quimica nova |
| Base de datos: | PERIÓDICA |
| Número de sistema: | 000313450 |
| ISSN: | 0100-4042 |
| Autores: | Saab, Sergio da Costa1 Martin-Neto, Ladislau2 |
| Instituciones: | 1Universidade Estadual de Ponta Grossa, Departamento de Fisica, Ponta Grossa, Parana. Brasil 2Empresa Brasileira de Pesquisa Agropecuaria, Sao Carlos, Sao Paulo. Brasil |
| Año: | 2007 |
| Periodo: | Abr |
| Volumen: | 30 |
| Número: | 2 |
| Paginación: | 260-263 |
| País: | Brasil |
| Idioma: | Portugués |
| Tipo de documento: | Artículo |
| Enfoque: | Experimental, aplicado |
| Resumen en inglés | In this work, seven samples of humic acids extracted from gleysoils were investigated. These studies, using NMR CP/MAS 13C techniques, did not show significant correlation between the E4/E6 ratio and the degree of aromaticity. However, dipolar dephasing (DD) measurements of condensed aromatic or substituted carbons showed a negative correlation of 0.94. Also, there was a good correlation between the amount of semiquinone free radicals measured by the EPR technique and condensed aromatic rings measured by NMR CP/MAS 13C with the DD technique. The content of semiquinone free radicals was quantified by EPR spectroscopy and was correlated with the humification (degree of aromaticity) of the humic substances. The results indicated that the E4/E6 ratio identifies the degree of aromatic rings condensation. It was also found that the degree of aromaticity, measured by NMR, as frequently presented in the literature (by conventional CP/MAS), underestimates aromatic rings in condensed structures |
| Disciplinas: | Química |
| Palabras clave: | Química analítica, Acidos húmicos, Anillos aromáticos, Desacoplamiento dipolar, Resonancia magnética nuclear |
| Keyword: | Chemistry, Analytical chemistry, Humic acids, Aromatic rings, Dipolar dephasing, Nuclear magnetic resonance |
| Texto completo: | Texto completo (Ver HTML) |
