An “Average” Structure Proposed for Soil Fulvic Acid Aided by Dept/Quat 13c NMR Pulse Techniques

13C NMR and mass spectrometry of soil organic matter

“…The percentage of SOM in the samples is increased. The soil-extracts may be investigated by solution-state NMR spectroscopy, which gives better resolution of the spectra, especially with the use of high¯eld NMR spectrometers and also one-and two-dimensional techniques [3,4,17]. Both humic (HH, HG) and fulvic (FH, FG) acids were isolated and investigated separately to obtain more information about the composition and chemical structure of the SOM in sample soils H and G. The 13 C NMR spectra of humic and fulvic acids demonstrated many overlapping resonances which were di±cult to resolve even at high¯eld (100.6 MHz for 13 C).…”

“…The results are presented in Table 1. The quantitative distribution (in %) of CH 3 , CH 2 , CH and C-quaternary carbons was calculated on the basis of the integral intensity of the spectral regions in the DEPT spectra and sub-spectra [3,4,22]. The sum total of the quantitative distribution (in %) of CH n (n = 0, 1, 2 and 3) for every one spectral area was compared to those obtained from the 13 C NMR spectra recorded using the inverse-gated decoupling technique.…”

“…It identi¯es partial structures of the SOM chemical components. Additional structural information for liquid extracts is obtained by the application of the NMR techniques of Distortionless Enhancement by Polarisation Transfer (DEPT), SEMUT-90 (sub-spectral editing using a multiple quantum trap) [3] and two-dimensional (2D) NMR experiments [1]. DEPT, SEMUT-90 and 2D J-resolved spectroscopy have been used previously to study aquatic humic substances [4].…”

Probe of cadmium(II) binding on soil fulvic acid investigated by113Cd NMR spectroscopy

“…Fulvic acid used in the experiment was isolated from air-dried soil from the Okchun Basin as described previously (23). Briefly, humic substances were extracted from air-dried soil (1.5 kg) with 15 dm3 of 0.1 mol dm-3 NaOH under N, atmosphere.…”

“…Other possible examples are those complexes of cadmium coordination by a neutral N donor: The minor sites of fulvic acid are said to include neutral N donors. The soil fulvic acid contained approximately 2.2% nitrogen, and the proposed average structure included a neutral N donor (23). The chemical shift changes of complexes of cadmium(I1) coordinated to carboxylic acids containing a neutral N donor (e.g., nicotinic, picolinic, and dipicolic acids) are shown in Fig.…”