Effect of residual vanadyl ions on the spectroscopic analysis of humic acids: a multivariate approach |
| |
| Authors: | E. H. Novotny,,H. Knicker,,L. Martin-Neto,R. B. V. Azeredo, & M. H. B. Hayes |
| |
| Affiliation: | Embrapa Solos, Rua Jardim Botânico, 1024, CEP 22460-000, Rio de Janeiro, RJ, Brazil; , Chemical and Environmental Sciences, University of Limerick, Limerick, Ireland; , Lehrstuhl für Bodenkunde, Technische Universität München, 85350 Freising-Weihenstephan, Germany; , Embrapa Instrumentação Agropecuária, Rua XV de Novembro, 1452, CEP 13560-970, São Carlos, SP, Brazil; , and Instituto de Química, Universidade Federal Fluminense, Outeiro de São João Batista, s/n°, Campus do Valonguinho, CEP 24020-150, Niterói, RJ, Brazil |
| |
| Abstract: | In a study of the vanadyl (VO2+)‐humic acids system, the residual vanadyl ion suppressed fluorescence and specific electron paramagnetic resonance (EPR) and NMR signals. In the case of NMR, the proton rotating frame relaxation times (T1ρH) indicate that this suppression is due to an inefficient H‐C cross polarization, which is a consequence of a shortening of T1ρH. Principal components analysis (PCA) facilitated the isolation of the effect of the VO2+ ion and indicated that the organic free radical signal was due to at least two paramagnetic centres and that the VO2+ ion preferentially suppressed the species whose electronic density is delocalized over O atoms (greater g‐factor). Additionally, the newly obtained variables (principal components – PC) indicated that, as the result of the more intense tillage a relative increase occurred in the accumulation of: (i) recalcitrant structures; (ii) lignin and long‐chain alkyl structures; and (iii) organic free radicals with smaller g‐factors. |
| |
| Keywords: | |
|
|
