Characterisation of the backbone structures of several fulvic acids using a novel selective chemical reduction method

Nimmagadda, Rama D.; McRae, Christopher

doi:10.1016/j.orggeochem.2007.02.016

Cited by 22 publications

(18 citation statements)

References 36 publications

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“…For initial characterization by GC, this PPL-DOM was chemically reduced with n -butylsilane ( n -BS) and a tris(pentafluorophenyl)borane [B(C 6 F 5 ) 3 ] catalyst ( 12 , 15 ). The reduction converts most oxygen-containing functional groups (for example, esters, carboxylic acids, and alcohols) to their respective hydrocarbon backbones (scheme S1) and makes PPL-DOM constituents amenable to separation by GC×GC.…”

Section: Resultsmentioning

confidence: 99%

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Carotenoids are the likely precursor of a significant fraction of marine dissolved organic matter

et al. 2017

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Section: Resultsmentioning

confidence: 99%

“…The reduction procedure directly followed Arakawa and Aluwihare ( 12 ), which was modeled after Nimmagadda and McRae ( 15 ). For model compound reductions, substrates (~2.5 mg) were transferred by syringe to a 2-ml single flame-dried vial equipped with a stir bar.…”

Section: Methodsmentioning

confidence: 99%

Carotenoids are the likely precursor of a significant fraction of marine dissolved organic matter

et al. 2017

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“…19,22,31,35,36 In contrast, early studies found recurring low m/z product ions (e.g., m/z 95, 97, 109, 111, 123, 125, 137, 139, 151, and 153) that were interpreted as a limited set of core structural units substituted with a set of functional groups, yet in different amounts and configurational types that would lead to highly diverse mixtures, thus opening an avenue to identify their precursors. 33,35,[37][38][39][40][41][42] Although many studies followed up on the core structure idea, 17,19,43,44 most recent studies mainly focus on similarities in the more abundant but non-indicative neutral losses, arguing that this reflects universal patterns of DOM diversification upon decomposition across environments. 22,23 From a stochastic standpoint, the occurrence of common neutral losses may not be surprising; for example, many structures contain hydroxyl groups that could yield H2O losses, and CO2 can originate from different functionalities despite carboxyl groups.…”

Section: Introductionmentioning

confidence: 99%

Mass difference matching crystallizes hidden molecular structures of dissolved organic matter from ultrahigh-resolution tandem mass spectra

Simon

Petras

Roth

et al. 2021

Preprint

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Ultrahigh-resolution mass spectrometry has revealed unprecedented detail of natural complex mixtures such as dissolved organic matter (DOM) on a molecular formula level but we lack information on the underlying structural complexity for full-scale identification. We applied a novel approach to decipher DOM’s characteristic chimeric tandem mass (MS2) spectra that represent multiple precursors of the same nominal mass. We calculated mass difference (Δm) matrices from precursor and product ions and matched them with reference Δm’s from 11280 library MS2 spectra and molecular structures. We found 1) indication for the presence of degraded phenolic plant metabolites, unknown N- and S-containing molecules, and missing elements in formula annotation, 2) weak support for postulated Van Krevelen structural domains, 3) multiple significant links between precursor properties, Δm matches, and chemodiversity. Our paper highlights Δm matching by MS2 as a promising tool to reveal novel structural information and molecular ecosystem imprints in complex mixtures like DOM.

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“…HS are the main component of soil organic matter (SOM) and play an important role in soil structure modification and soil fertility improvement, and functional groups of soil clay fractions play a key role in determining the adsorption affinity and hence retention of dissolved organic carbon in soils (Mandeep et al 2017). HS commonly form organic–inorganic complexes to improve their stability, which reduces their greenhouse gas emissions, by combining with iron, aluminum oxides, and clay minerals in soils (Jung et al 2005; Majzik and Tombacz 2007; Nimmagadda and Mcrae 2007). The HS in soils commonly consist of fulvic acids (FAs), humic acids (HAs), and humin.…”

Section: Introductionmentioning

confidence: 99%

Structural characteristics of humic substances in buried ancient paddy soils as revealed by 13C NMR spectroscopy

Liu

Zhou

Cui

et al. 2019

Environ Geochem Health

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The study of organic matter in ancient paddy soils is helpful for understanding the influence of human activities on soil carbon sequestration and global climate change. However, little information on the spatial distribution and structural characteristics of the humic substances (HS) in ancient paddy soils is available. The spatial distributions of humic acids (HAs) and fulvic acids (FAs) in ancient paddy soils and modern cultivated paddy soils at the Shanlonggang site on the Liyang Plain were investigated, and the associated structures were characterized by using 13C nuclear magnetic resonance (NMR). The 13C NMR spectra revealed the following carbon types in HAs and FAs in both types of paddy soil in order of decreasing abundance: O-alkyl carbon (ranging from 39.7 to 51.8% and from 42.6 to 50.9%, respectively) ≥ alkyl carbon (ranging from 16.8 to 23.5% and from 15.7 to 22.4%, respectively) ≈ carboxyl carbon (ranging from 13.3 to 19.3% and from 16.9 to 22.0%, respectively) > aromatic carbon (ranging from 12.8 to 23.5% and from 10.0 to 17.2%, respectively). Moreover, the degree of aromaticity of HA was higher than that of FA in both soil samples. The humic constituents of the buried ancient paddy soils were less aromatic and oxidized than those of the modern cultivated paddy soils. The organic carbon in the ancient paddy soils was also less aromatic and oxidized than that in the modern cultivated paddy soils, suggesting that the structures of the HS in the ancient paddy soils were relatively simple. The results of this study provide new insights into the effect of secondary paddy soil formation on the spatial distribution, structural characteristics, and stability mechanisms of the HS in ancient paddy soils.

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Characterisation of the backbone structures of several fulvic acids using a novel selective chemical reduction method

Cited by 22 publications

References 36 publications

Carotenoids are the likely precursor of a significant fraction of marine dissolved organic matter

Carotenoids are the likely precursor of a significant fraction of marine dissolved organic matter

Mass difference matching crystallizes hidden molecular structures of dissolved organic matter from ultrahigh-resolution tandem mass spectra

Structural characteristics of humic substances in buried ancient paddy soils as revealed by 13C NMR spectroscopy

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