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Structural insight into conifer forest topsoil dissolved organic matter (Wetzstein, Germany) by Orbitrap tandem MS mass difference matching

Ultrahigh-resolution Fourier transform tandem mass spectrometry was employed to reveal novel structural detail of the natural complex mixture dissolved organic matter (DOM) that is found ubiquitously in soils and rivers. We developed and evaluated a novel approach to decipher the structural detail that is encrypted in DOM. A DOM sample from a spruce forest (Wetzstein, Germany, 50° 27' 13" N; 11° 27' 27" E; 785 meter above sea level) was used as a representative biodegraded DOM mixture of high complexity and measured by direct-injection tandem mass spectrometry (DI-ESI-Orbitrap-MS/MS). The unknowns in DOM were then compared with indicative tandem MS features (mass differences, "Δm" features) from known standard compounds (14 phenolic standard substances measured in parallel, and 11280 library mass spectra available from the java-based software framework SIRIUS) and natural product and in-silico structure suggestions. The dataset consists of six subsets (Data Set ds01 - ds06), all of which are xlsx files.

Structural insight into conifer forest topsoil and blackwater dissolved organic matter by Orbitrap tandem MS mass difference matching

Ultrahigh-resolution Fourier transform tandem mass spectrometry was employed to reveal novel structural detail of the natural complex mixture dissolved organic matter (DOM) that is found ubiquitously in soils and rivers. We developed and evaluated a novel approach to decipher the structural detail that is encrypted in DOM. One DOM sample from a spruce forest (Wetzstein, Germany, 50° 27' 13" N; 11° 27' 27" E; 785 meter above sea level) and Suwannee River Natural Organic Matter (SRNOM, purchased from International Humic Substances Society as isolate 2R101N; details given in Green et al. 2015, Environm Eng Sci 32, 1) were used as representative biodegraded DOM mixtures of high complexity and measured by direct-injection tandem mass spectrometry (DI-ESI-Orbitrap-MS/MS). The unknowns in DOM were then compared with indicative tandem MS features (mass differences, "dm" features, written with greek letter delta instead of d) from known standard compounds (14 phenolic standard substances measured in parallel, and 11477 library mass spectra available from the java-based software framework SIRIUS which included nearly 18000 unique molecular structures) and natural product and in-silico structure suggestions. The dataset consists of seven subsets (Data Set S1 - S7), all of which are xlsx files. "Data Set S1", contains the standard compound data and fragmentation sensitivities (14 phenolic standards) and general information on the analyzed parts of the DOM mass spectrum (molecular indices, number of precursors, number of product ions). Data Sets S2 through S5 contain the aligned DOM molecular composition data obtained at different collision energies for four mass windows ("Data Set S2", m/z 241; "Data Set S3", m/z 301; "Data Set S4", m/z 361; "Data Set S5", m/z 417) and include mass difference matching results (non-indicative dm features, standard compound (14 phenolics) dm features, and SIRIUS library spectra Δm features). "Data Set S6" contains the full dm feature lists and several data tables on individual DOM precursor properties (for example, aggregated matching results for indicative dm features (incl. N- and S-containing precursors), DOM precursor fragmentation sensitivity data, two-way clustering data of precursors and dm features, and structure suggestions classified into broader structural families ("scaffolds"). "Data Set S7" contains the results of a two-way clustering analysis using 725 SIRIUS-annotated dm features. In this dataset, the dm data is used to estimate structural compositions of individual DOM precursor ions. More details can be found in the related manuscript by the same authors.

Raw mass spectrometric data to dissolved organic matter molecular composition data of exemplary water masses resolved by online LC-FT-ICR-MS

The unique chromatographic behaviour of DOM was investigated on three exemplary water samples representing coastal DOM, oceanic surface DOM and oceanic refractory DOM. Weddell Sea surface (30 m depth, oceanic surface DOM) and deep water (1356 m depth, refractory DOM) was sampled with a rosette sampler on RV Polarstern during ANT XXII/2 (station PS67/006-130, latitude -67.5633, longitude -55.3448) and are described elsewhere (El Naggar et al., 2007; Koch et al., 2008). Coastal DOM is routinely extracted from southern North Sea (latitude 54.1447, longitude 7.8711) and used as an in-house laboratory standard. Mass spectra were obtained with liquid chromatography coupled to a Fourier-transform ion cyclotron resonance mass spectrometer (LC-FT-ICR-MS) with negative electrospray ionisation. A 7 Tesla scimaX MRMS system (Bruker Daltonics GmbH & Co. KG, Bremen, Germany) was coupled to an ultra-performance liquid chromatography system (UPLC, Elute LC, Bruker Daltonics GmbH & Co. KG, Bremen, Germany). Reversed phase chromatography was done with a C18 column (Waters AQUITY 2 x 100 mm, 1.7 µm) column at 0.3 mL min 1 and a linear gradient: A (ultrapure water, 4 mmol L 1 ammonium formate) 2 min: 99 %, 11 min: 0 %, 14.9 min: 99 %; B (MeOH, 4 mmol L 1 ammonium formate) 2 min: 1 %, 11 min: 100 %, 14.5 min 100 %, 14.9 min 1 %. The exact mass lists and intensities of the 1.1 min binned scans were exported with the DataAnalysis 5.3 software package (Bruker Daltonics GmbH & Co. KG, Bremen, Germany).

Raw mass spectrometric data to dissolved organic matter molecular composition data of exemplary water masses resolved by online LC-FT-Orbitrap-MS

The unique chromatographic behaviour of DOM was investigated on three exemplary water samples representing coastal DOM, oceanic surface DOM and oceanic refractory DOM. Weddell Sea surface (30 m depth, oceanic surface DOM) and deep water (1356 m depth, refractory DOM) was sampled with a rosette sampler on RV Polarstern during ANT XXII/2 (station PS67/006-130, latitude -67.5633, longitude -55.3448) and are described elsewhere (El Naggar et al., 2007; Koch et al., 2008). Coastal DOM is routinely extracted from southern North Sea (latitude 54.1447, longitude 7.8711) and used as an in-house laboratory standard. Mass spectra were obtained with liquid chromatography coupled to a Fourier-transform Orbitrap mass spectrometer (LC-FT-Orbitrap-MS) with negative electrospray ionisation. A Q-Exactive Plus (Thermo Fisher Scientific, Bremen, Germany) was coupled to an ultra-performance liquid chromatography system (UPLC, Vanquish, Thermo Fisher Scientific, Bremen, Germany). Reversed phase chromatography was done with a C18 column (Waters AQUITY 2 x 100 mm, 1.7 µm) column at 0.3 mL min 1 and a linear gradient: A (ultrapure water, 4 mmol L 1 ammonium formate) 2 min: 99 %, 11 min: 0 %, 14.9 min: 99 %; B (MeOH, 4 mmol L 1 ammonium formate) 2 min: 1 %, 11 min: 100 %, 14.5 min 100 %, 14.9 min 1 %. The exact mass lists and intensities of the 1.1 min binned scans were exported with the Xcalibur software package (Thermo Electron Corporation).

Annotated and filtered molecular formulas associated with dissolved organic matter molecular composition data of exemplary water masses resolved by online LC-FT-ICR-MS

The unique chromatographic behaviour of DOM was investigated on three exemplary water samples representing coastal DOM, oceanic surface DOM and oceanic refractory DOM. Weddell Sea surface (30 m depth, oceanic surface DOM) and deep water (1356 m depth, refractory DOM) was sampled with a rosette sampler on RV Polarstern during ANT XXII/2 (station PS67/006-130, latitude -67.5633, longitude -55.3448) and are described elsewhere (El Naggar et al., 2007; Koch et al., 2008). Coastal DOM is routinely extracted from southern North Sea (latitude 54.1447, longitude 7.8711) and used as an in-house laboratory standard. Mass spectra were obtained with liquid chromatography coupled to a Fourier-transform ion cyclotron resonance mass spectrometer (LC-FT-ICR-MS) with negative electrospray ionisation. A 7 Tesla scimaX MRMS system (Bruker Daltonics GmbH & Co. KG, Bremen, Germany) was coupled to an ultra-performance liquid chromatography system (UPLC, Elute LC, Bruker Daltonics GmbH & Co. KG, Bremen, Germany). Reversed phase chromatography was done with a C18 column (Waters AQUITY 2 x 100 mm, 1.7 µm) column at 0.3 mL min 1 and a linear gradient: A (ultrapure water, 4 mmol L 1 ammonium formate) 2 min: 99 %, 11 min: 0 %, 14.9 min: 99 %; B (MeOH, 4 mmol L 1 ammonium formate) 2 min: 1 %, 11 min: 100 %, 14.5 min 100 %, 14.9 min 1 %. The exact mass lists and intensities of the 1.1 min binned scans were exported with the DataAnalysis 5.3 software package (Bruker Daltonics GmbH & Co. KG, Bremen, Germany). Scans were calibrated with an in-house script. Molecular formulas were assigned with the following elemental composition: 12C≤∞1H≤∞16O≤∞14N≤232S≤1 within 0.3 ppm mass deviation, and filtered with the Ultra Mass Explorer (UME, www.awi.de/en/ume, (Leefmann et al., 2019)).

Annotated and filtered molecular formulas associated with dissolved organic matter molecular composition data of exemplary water masses resolved by online LC-FT-Orbitrap-MS

The unique chromatographic behaviour of DOM was investigated on three exemplary water samples representing coastal DOM, oceanic surface DOM and oceanic refractory DOM. Weddell Sea surface (30 m depth, oceanic surface DOM) and deep water (1356 m depth, refractory DOM) was sampled with a rosette sampler on RV Polarstern during ANT XXII/2 (station PS67/006-130, latitude -67.5633, longitude -55.3448) and are described elsewhere (El Naggar et al., 2007; Koch et al., 2008). Coastal DOM is routinely extracted from southern North Sea (latitude 54.1447, longitude 7.8711) and used as an in-house laboratory standard. Mass spectra were obtained with liquid chromatography coupled to a Fourier-transform Orbitrap mass spectrometer (LC-FT-Orbitrap-MS) with negative electrospray ionisation. A Q-Exactive Plus (Thermo Fisher Scientific, Bremen, Germany) was coupled to an ultra-performance liquid chromatography system (UPLC, Vanquish, Thermo Fisher Scientific, Bremen, Germany).Reversed phase chromatography was done with a C18 column (Waters AQUITY 2 x 100 mm, 1.7 µm) column at 0.3 mL min 1 and a linear gradient: A (ultrapure water, 4 mmol L 1 ammonium formate) 2 min: 99 %, 11 min: 0 %, 14.9 min: 99 %; B (MeOH, 4 mmol L 1 ammonium formate) 2 min: 1 %, 11 min: 100 %, 14.5 min 100 %, 14.9 min 1 %. The exact mass lists and intensities of the 1.1 min binned scans were exported with the Xcalibur software package (Thermo Electron Corporation). Scans were calibrated with an in-house script. Molecular formulas were assigned with the following elemental composition: 12C≤∞1H≤∞16O≤∞14N≤232S≤1 within 0.8 ppm mass deviation, and filtered with the Ultra Mass Explorer (UME, www.awi.de/en/ume, (Leefmann et al., 2019)).

Dissolved organic matter molecular composition data of exemplary marine water masses resolved by online LC-MS

The unique chromatographic behaviour of DOM was investigated on three exemplary water samples representing coastal DOM, oceanic surface DOM and oceanic refractory DOM. Weddell Sea surface (30 m depth, oceanic surface DOM) and deep water (1356 m depth, refractory DOM) was sampled with a rosette sampler on RV Polarstern during ANT XXII/2 (station PS67/006-130, latitude -67.5633, longitude -55.3448) and are described elsewhere (El Naggar et al., 2007; Koch et al., 2008). 160 L sea water was filtered with 0.2 µm filter cartridges, acidified to pH 2 and pumped through 60 mL solid phase extraction cartridges (PPL, 5 g). DOM was eluted with 40 mL MeOH and stored at -18 °C. Coastal DOM is routinely extracted from southern North Sea (latitude 54.1447, longitude 7.8711) and used as an in-house laboratory standard. Sea water was filtered over 0.2 µm PTFE (Whatman), acidified to pH 2 and extracted with PPL cartridges. After elution with methanol, extracts are stored at -18 °C until measurement to minimize esterification (Flerus et al., 2011). The molecular composition was obtained by two mass spectrometric platforms with negative electrospray ionisation: 1) Fourier Transform Orbitrap mass spectrometer (FT-Orbitrap-MS; Q-Exactive Plus, Thermo Fisher Scientific, Bremen, Germany) coupled to ultra-high performance liquid chromatography (UPLC, Vanquish, Thermo Fisher Scientific, Bremen, Germany); 2) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS; 7 Tesla scimaX MRMS system, Bruker Daltonics GmbH & Co. KG, Bremen, Germany) coupled to UPLC (Elute LC, Bruker Daltonics GmbH & Co. KG, Bremen, Germany). Reversed phase chromatography was done with a C18 column (Waters AQUITY 2 x 100 mm, 1.7 µm) column at 0.3 mL min 1 and a linear gradient: A (ultrapure water, 4 mmol L 1 ammonium formate) 2 min: 99 %, 11 min: 0 %, 14.9 min: 99 %; B (MeOH, 4 mmol L 1 ammonium formate) 2 min: 1 %, 11 min: 100 %, 14.5 min 100 %, 14.9 min 1 %.

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