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Effect of residual vanadyl ions on the spectroscopic analysis of humic acids: a multivariate approach
Author(s) -
Novotny E. H.,
Knicker H.,
MartinNeto L.,
Azeredo R. B. V.,
Hayes M. H. B.
Publication year - 2008
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2007.00983.x
Subject(s) - electron paramagnetic resonance , chemistry , delocalized electron , ion , paramagnetism , radical , analytical chemistry (journal) , nuclear magnetic resonance , organic chemistry , physics , quantum mechanics
Summary In a study of the vanadyl (VO 2+ )‐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 (T 1ρ H) indicate that this suppression is due to an inefficient H‐C cross polarization, which is a consequence of a shortening of T 1ρ H. Principal components analysis (PCA) facilitated the isolation of the effect of the VO 2+ ion and indicated that the organic free radical signal was due to at least two paramagnetic centres and that the VO 2+ 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.