Effect of residual vanadyl ions on the spectroscopic analysis of humic acids: a multivariate approach

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...

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Bibliographic Details
Published in:European journal of soil science 2008-06, Vol.59 (3), p.439-444
Main Authors: Novotny, E.H, Knicker, H, Martin-N.eto, L, Azeredo, R.B.V, Hayes, M.H.B
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Biological and medical sciences
Earth sciences
Earth, ocean, space
Exact sciences and technology
Fundamental and applied biological sciences. Psychology
Soil science
Soils
Surficial geology
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Summary: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.
ISSN:1351-0754
1365-2389
DOI:10.1111/j.1365-2389.2007.00983.x