Characterization of Burned Soil Organic Matter via Sequential Solvent Extractions and 21 T FT-ICR Mass Spectrometry with Electrospray and Atmospheric Pressure Photoionization

Holly K. Roth; Amy M. McKenna; Martha L. Aguilera; Jacob P. VanderRoest; Huan Chen; Thomas Borch

doi:10.1021/acs.analchem.5c04154

Characterization of Burned Soil Organic Matter via Sequential Solvent Extractions and 21 T FT-ICR Mass Spectrometry with Electrospray and Atmospheric Pressure Photoionization

Holly K. Roth
, Amy M. McKenna
, Martha L. Aguilera
, Jacob P. VanderRoest
, Huan Chen
, Thomas Borch

Research output: Contribution to journal › Article › peer-review

Abstract

Wildfires significantly alter soil organic matter (SOM) composition, generating complex mixtures of polar and nonpolar compounds which are difficult to analyze. This study combines sequential extractions with electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) followed by 21 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to improve the molecular characterization of SOM from burned soils. Soils were extracted first with water and then Soxhlet extracted with organic solvents (acetone/cyclohexane and methanol/toluene/tetrahydrofuran). The compositional range of species identified by positive and negative ESI was expanded by 8–62%, and APPI enabled the detection of hydrocarbons and nitrogen-containing species that were largely undetected by ESI alone. Among the identified compounds, molecular formulas consistent with biomarkers such as stigmasta-3,5-diene, a plant-derived sterol degradation product, were present only in the organic solvents. Stigmasta-3,5-diene and similar compounds have been observed after fire events across various vegetation types, including forest ecosystems. Highly abundant compounds detected at four double bond equivalents (e.g., 25-azacoprostane) may represent sterol interrupters or cholesterol metabolism inhibitors, potentially serving as additional biomarkers for fire conditions. The calculated nominal oxidation state of carbon (NOSC) revealed distinct groupings based on solvent type and ionization mode, emphasizing the selective extraction of less labile organic matter by organic solvents compared to water. These results highlight the critical role of sequential solvent extraction and diverse data analysis strategies in advancing the understanding of fire-impacted SOM chemistry and provide a framework for biomarker discovery in environmental monitoring and biogeochemical studies.

Original language	English
Pages (from-to)	24040-24049
Number of pages	10
Journal	Analytical Chemistry
Volume	97
Issue number	43
DOIs	https://doi.org/10.1021/acs.analchem.5c04154
State	Published - 2025
Externally published	Yes

Funding

This research was funded by the National Science Foundation 2114868 and the USDA National Institute of Food Agriculture through AFRI grant no. 2021-67019-34608. A portion of the work was performed at the National High Magnetic Field Laboratory ICR User Facility, which is supported by the National Science Foundation Division of Chemistry and Division of Material Research through DMR-1644779 and the State of Florida. The authors thank Chuck Rhoades and Tim Fegel from the Rocky Mountain Research Station for providing soil for the pyrocosm burns and the Poudre Fire Authority for their support during the burns.Figure 1andhttps://pubs.acs.org/doi/suppl/10.1021/acs.analchem.5c04154/suppl_file/ac5c04154_si_001.pdfwere created withBioRender.com. This research was funded by the National Science Foundation 2114868 and the USDA National Institute of Food Agriculture through AFRI grant no. 2021-67019-34608. A portion of the work was performed at the National High Magnetic Field Laboratory ICR User Facility, which is supported by the National Science Foundation Division of Chemistry and Division of Material Research through DMR-1644779 and the State of Florida. The authors thank Chuck Rhoades and Tim Fegel from the Rocky Mountain Research Station for providing soil for the pyrocosm burns and the Poudre Fire Authority for their support during the burns. and Figure S1 were created with BioRender.com . Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05–00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( https://www.energy.gov/doe-public-access-plan ).

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10.1021/acs.analchem.5c04154

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@article{9cb2a614153a4daaa54c96b02d2bc790,

title = "Characterization of Burned Soil Organic Matter via Sequential Solvent Extractions and 21 T FT-ICR Mass Spectrometry with Electrospray and Atmospheric Pressure Photoionization",

abstract = "Wildfires significantly alter soil organic matter (SOM) composition, generating complex mixtures of polar and nonpolar compounds which are difficult to analyze. This study combines sequential extractions with electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) followed by 21 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to improve the molecular characterization of SOM from burned soils. Soils were extracted first with water and then Soxhlet extracted with organic solvents (acetone/cyclohexane and methanol/toluene/tetrahydrofuran). The compositional range of species identified by positive and negative ESI was expanded by 8–62\%, and APPI enabled the detection of hydrocarbons and nitrogen-containing species that were largely undetected by ESI alone. Among the identified compounds, molecular formulas consistent with biomarkers such as stigmasta-3,5-diene, a plant-derived sterol degradation product, were present only in the organic solvents. Stigmasta-3,5-diene and similar compounds have been observed after fire events across various vegetation types, including forest ecosystems. Highly abundant compounds detected at four double bond equivalents (e.g., 25-azacoprostane) may represent sterol interrupters or cholesterol metabolism inhibitors, potentially serving as additional biomarkers for fire conditions. The calculated nominal oxidation state of carbon (NOSC) revealed distinct groupings based on solvent type and ionization mode, emphasizing the selective extraction of less labile organic matter by organic solvents compared to water. These results highlight the critical role of sequential solvent extraction and diverse data analysis strategies in advancing the understanding of fire-impacted SOM chemistry and provide a framework for biomarker discovery in environmental monitoring and biogeochemical studies.",

author = "Roth, \{Holly K.\} and McKenna, \{Amy M.\} and Aguilera, \{Martha L.\} and VanderRoest, \{Jacob P.\} and Huan Chen and Thomas Borch",

note = "Publisher Copyright: {\textcopyright} 2025 American Chemical Society",

year = "2025",

doi = "10.1021/acs.analchem.5c04154",

language = "English",

volume = "97",

pages = "24040--24049",

journal = "Analytical Chemistry",

issn = "0003-2700",

publisher = "American Chemical Society",

number = "43",

}

Characterization of Burned Soil Organic Matter via Sequential Solvent Extractions and 21 T FT-ICR Mass Spectrometry with Electrospray and Atmospheric Pressure Photoionization. / Roth, Holly K.; McKenna, Amy M.; Aguilera, Martha L. et al.
In: Analytical Chemistry, Vol. 97, No. 43, 2025, p. 24040-24049.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Characterization of Burned Soil Organic Matter via Sequential Solvent Extractions and 21 T FT-ICR Mass Spectrometry with Electrospray and Atmospheric Pressure Photoionization

AU - Roth, Holly K.

AU - McKenna, Amy M.

AU - Aguilera, Martha L.

AU - VanderRoest, Jacob P.

AU - Chen, Huan

AU - Borch, Thomas

PY - 2025

Y1 - 2025

N2 - Wildfires significantly alter soil organic matter (SOM) composition, generating complex mixtures of polar and nonpolar compounds which are difficult to analyze. This study combines sequential extractions with electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) followed by 21 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to improve the molecular characterization of SOM from burned soils. Soils were extracted first with water and then Soxhlet extracted with organic solvents (acetone/cyclohexane and methanol/toluene/tetrahydrofuran). The compositional range of species identified by positive and negative ESI was expanded by 8–62%, and APPI enabled the detection of hydrocarbons and nitrogen-containing species that were largely undetected by ESI alone. Among the identified compounds, molecular formulas consistent with biomarkers such as stigmasta-3,5-diene, a plant-derived sterol degradation product, were present only in the organic solvents. Stigmasta-3,5-diene and similar compounds have been observed after fire events across various vegetation types, including forest ecosystems. Highly abundant compounds detected at four double bond equivalents (e.g., 25-azacoprostane) may represent sterol interrupters or cholesterol metabolism inhibitors, potentially serving as additional biomarkers for fire conditions. The calculated nominal oxidation state of carbon (NOSC) revealed distinct groupings based on solvent type and ionization mode, emphasizing the selective extraction of less labile organic matter by organic solvents compared to water. These results highlight the critical role of sequential solvent extraction and diverse data analysis strategies in advancing the understanding of fire-impacted SOM chemistry and provide a framework for biomarker discovery in environmental monitoring and biogeochemical studies.

AB - Wildfires significantly alter soil organic matter (SOM) composition, generating complex mixtures of polar and nonpolar compounds which are difficult to analyze. This study combines sequential extractions with electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) followed by 21 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to improve the molecular characterization of SOM from burned soils. Soils were extracted first with water and then Soxhlet extracted with organic solvents (acetone/cyclohexane and methanol/toluene/tetrahydrofuran). The compositional range of species identified by positive and negative ESI was expanded by 8–62%, and APPI enabled the detection of hydrocarbons and nitrogen-containing species that were largely undetected by ESI alone. Among the identified compounds, molecular formulas consistent with biomarkers such as stigmasta-3,5-diene, a plant-derived sterol degradation product, were present only in the organic solvents. Stigmasta-3,5-diene and similar compounds have been observed after fire events across various vegetation types, including forest ecosystems. Highly abundant compounds detected at four double bond equivalents (e.g., 25-azacoprostane) may represent sterol interrupters or cholesterol metabolism inhibitors, potentially serving as additional biomarkers for fire conditions. The calculated nominal oxidation state of carbon (NOSC) revealed distinct groupings based on solvent type and ionization mode, emphasizing the selective extraction of less labile organic matter by organic solvents compared to water. These results highlight the critical role of sequential solvent extraction and diverse data analysis strategies in advancing the understanding of fire-impacted SOM chemistry and provide a framework for biomarker discovery in environmental monitoring and biogeochemical studies.

UR - https://www.scopus.com/pages/publications/105024072826

U2 - 10.1021/acs.analchem.5c04154

DO - 10.1021/acs.analchem.5c04154

M3 - Article

AN - SCOPUS:105024072826

SN - 0003-2700

VL - 97

SP - 24040

EP - 24049

JO - Analytical Chemistry

JF - Analytical Chemistry

IS - 43

ER -

Characterization of Burned Soil Organic Matter via Sequential Solvent Extractions and 21 T FT-ICR Mass Spectrometry with Electrospray and Atmospheric Pressure Photoionization

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