| 1. |
- Hawkes, Jeffrey A., et al.
(författare)
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Evaluation of the Orbitrap Mass Spectrometer for the Molecular Fingerprinting Analysis of Natural Dissolved Organic Matter
- 2016
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 88:15, s. 7698-7704
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the application of the LTQ-Orbitrap mass spectrometer (LTQ-Velos Pro, Thermo Fisher) for resolving complex mixtures of natural aquatic dissolved organic matter (DOM) and compared this technique to the more established state-of-the-art technique, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS, Bruker Daltonics), in terms of the distribution of molecular masses detected and the reproducibility of the results collected. The Orbitrap was capable of excellent reproducibility: Bray-Curtis dissimilarity between duplicate measurements was 2.85 +/- 0.42% (mean +/- standard deviation). The Orbitrap was also capable of the detection of most major ionizable organic molecules in typical aquatic mixtures, with the exception of most sulfur and phosphorus containing masses. This result signifies that the Orbitrap is an appropriate technique for the investigation of very subtle biogeochemical processing of bulk DOM. The lower costs (purchase and maintenance) and wider availability of Orbitrap mass spectrometers in university departments means that the tools necessary for research into DOM processing at the molecular level should be accessible to a much wider group of scientists than before. The main disadvantage of the technique is that substantially fewer molecular formulas can be resolved from a complex mixture (roughly one third as many), meaning some loss of information. In balance, most biogeochemical studies that aim at molecularly fingerprinting the source of natural DOM could be satisfactorily carried out with Orbitrap mass spectrometry. For more targeted metabolomic studies where individual compounds are traced through natural systems, FTICR-MS remains advantageous.
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| 2. |
- Hawkes, Jeffrey A., et al.
(författare)
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Extreme isomeric complexity of dissolved organic matter found across aquatic environments
- 2018
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Ingår i: Limnology and Oceanography Letters. - : Wiley. - 2378-2242. ; 3:2, s. 21-30
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Tidskriftsartikel (refereegranskat)abstract
- The natural aquatic environment contains an enormous pool of dissolved reduced carbon, present as ultra‐complex mixtures that are constituted by an unknown number of compounds at vanishingly small concentrations. We attempted to separate individual structural isomers from several samples using online reversed‐phase chromatography with selected ion monitoring/tandem mass spectrometry, but found that isomeric complexity still presented a boundary to investigation even after chromatographic simplification of the samples. However, it was possible to determine that the structural complexity differed among samples. Our results also suggest that extreme structural complexity was a ubiquitous feature of dissolved organic matter (DOM) in all aquatic systems, meaning that this diversity may play similar roles for recalcitrance and degradation of DOM in all tested environments.
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| 3. |
- Patriarca, Claudia, et al.
(författare)
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Character and environmental lability of cyanobacteria-derived dissolved organic matter
- 2021
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 66:2, s. 496-509
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Tidskriftsartikel (refereegranskat)abstract
- Autotrophic dissolved organic matter (DOM) is central to the carbon biogeochemistry of aquatic systems, and the full complexity of autotrophic DOM has not been extensively studied, particularly by high-resolution mass spectrometry (HRMS). Terrestrial DOM tends to dominate HRMS studies in freshwaters due to the propensity of such compounds to ionize by negative mode electrospray, and possibly also because ionizable DOM produced by autotrophy is decreased to low steady-state concentrations by heterotrophic bacteria. In this study, we investigated the character of DOM produced by the widespread cyanobacteria Microcystis aeruginosa using high-pressure liquid chromatography—electrospray ionization—high-resolution mass spectrometry. M. aeruginosa produced thousands of detectable compounds in axenic culture. These compounds were chromatographically resolved and the majority were assigned to aliphatic formulas with a broad polarity range. We found that the DOM produced by M. aeruginosa was highly susceptible to removal by heterotrophic freshwater bacteria, supporting the hypothesis that this autotroph-derived organic material is highly labile and accordingly only seen at low concentrations in natural settings.
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| 4. |
- Patriarca, Claudia, 1986-
(författare)
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Characterisation of natural dissolved organic matter with liquid chromatography and high resolution mass spectrometry
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dissolved organic matter (DOM) is one of the most heterogeneous and complex mixture on Earth. DOM plays a crucial role in biogeochemical processes on the global scale and it is essential to sustain and regulate the biological processes in aquatic ecosystems. DOM originates from a multitude of biological, physical and chemical transformations, leading to its phenomenal chemical diversity. In order to understand and predict its effect on the global carbon cycle, an intimate characterization at molecular level is necessary. The investigation of the extraordinary complexity of the DOM mixture represents a compelling challenge for analytical chemistry. The focus of this thesis was the development of methods for the characterization of DOM in natural waters. High resolution mass spectrometry (HRMS), was combined with high pressure liquid chromatography (HPLC) and electrospray ionization (ESI), to investigate the chemical diversity of DOM. The first study demonstrated that cutting-edge techniques (such as the Fourier-transform ion cyclotron resonance mass spectrometer - FTICR-MS), are not indispensable to disclose essential information on the DOM molecular composition, in fact the Orbitrap mass analyser is a suitable alternative for the analysis of complex natural mixtures. In the second study, the potential benefits offered by the online coupling of HPLC and HRMS instruments were explored, revealing significant advantages in terms of analysis time, achievable information and versatility of the method. The advantages of online separation were further confirmed in the third study, focused on the characterization of autochthonous labile DOM. Chromatographically resolved profiles emerged from the bulk-DOM, allowing the monitoring of labile autochthonous components in presence of heterotrophic bacteria. Despite the advantages achieved by the application of online separation, a strong limiting factor in DOM characterization is the ESI source, suitable only for the analysis of the DOM fraction susceptible to ionization. In the last study, the extent of the DOM material prone to ionization was estimated, revealing the occurrence of an extensive portion of the material resistant to routinely employed ESI approach. The full characterization of DOM is still an open challenge and the combination of multiple techniques is fundamental to unravel is extreme intricacy.
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| 5. |
- Patriarca, Claudia
(författare)
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Characterization of dissolved organic matter : An analytical challenge
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dissolved organic matter (DOM) is the prevalent form of organic carbon in most aquatic environments. It is an ultra-complex mixture that plays a crucial role in global carbon cycling. Despite its importance it is still poorly understood due to its extreme heterogeneity and intricacy. Major advances in chemical characterization of DOM were possible with the introduction of high-resolution mass spectrometry (HRMS). This technique, in combination with direct infusion (DI) as sample introduction, is the most powerful tool for the DOM analysis to date. A compelling alternative to DI is represented by upfront separation with liquid chromatography (LC); however, current techniques involve only offline LC-HRMS approaches, which exhibit important logistical drawbacks, making DOM analysis more challenging.The aim of the presented studies was to develop new methods able to enhance the analysis of the dissolved organic matter and enable a wider range of researchers to participate in the advancement of this field.In the first study, the application of the Orbitrap mass spectrometer for resolving complex DOM mixtures was investigated and the results were compared to the more established state-of-the-art technique, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The Orbitrap was capable of excellent reproducibility and detection of the majority of ionizable organic molecules in typical aquatic mixtures. The main disadvantage of the technique is that fewer molecular formulas can be resolved and detected because of lower resolution and sensitivity. This means that many sulfur peaks and all phosphorous containing peaks are not determined. Despite this drawback, our results suggest that the Orbitrap is an appropriate technique for the investigation of very subtle biogeochemical processing of bulk DOM. The lower costs (purchase and maintenance) and wider availability of Orbitrap mass spectrometers allow a greater number of laboratories to participate in the characterization of DOM.In the second study, the first online method involving reverse phase chromatography and ultrahigh resolution mass spectrometry for the analysis of DOM was developed. This method overcomes the disadvantages of typical offline approaches. It enhances enormously the amount of information achievable in a single run, maintaining high resolution data, reducing analysis time and potential contamination. The introduction of in silico fractionation makes the method extremely flexible, allowing an easy, fast, and detailed comparison of DOM samples from a variety of sources.
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| 6. |
- Patriarca, Claudia, et al.
(författare)
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High Molecular Weight Spectral Interferences in Mass Spectra of Dissolved Organic Matter
- 2021
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Ingår i: Journal of the American Society for Mass Spectrometry. - : American Chemical Society (ACS). - 1044-0305 .- 1879-1123. ; 32:1, s. 394-397
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigate interferences that appear in molecular mass spectra from aquatic samples. The interferences are identified as doubly charged ions originating from high molecular weight material, which is especially abundant in terrestrial samples. The interferences could be incorrectly assigned to singly charged formulas with high aromaticity and heteroatom content, as the mass error from such formulas can be less than 1 ppm. We propose a strategy for filtering the interference peaks from mass lists based on the presence of their equivalent isotopologue peaks at mass defects of similar to 0.5 Da.
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| 7. |
- Patriarca, Claudia, et al.
(författare)
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Investigating the Ionization of Dissolved Organic Matter by Electrospray
- 2020
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:20, s. 14210-14218
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Tidskriftsartikel (refereegranskat)abstract
- Electrospray ionization (ESI) operating in the negative mode coupled to high-resolution mass spectrometry is the most popular technique for the characterization of dissolved organic matter (DOM). The vast molecular heterogeneity and the functional group diversity of this complex mixture prevents the efficient ionization of the organic material by a single ionization source, so the presence of uncharacterized material is unavoidable. The extent of this poorly ionizable pool of carbon is unknown, is presumably variable between samples, and can only be assessed by the combination of analysis with a uniform detection method. Charged aerosol detection (CAD), whose response is proportional to the amount of nonvolatile material and is independent from the physicochemical properties of the analytes, is a suitable candidate. In this study, a fulvic acid mixture was fractionated and analyzed by high-pressure liquid chromatography–mass spectrometry in order to investigate the polarity and size distributions of highly and poorly ionizable material in the sample. Additionally, DOM samples of terrestrial and marine origins were analyzed to evaluate the variability of these pools across the land–sea aquatic continuum. The relative response factor values indicated that highly ionizable components of aquatic DOM mixtures are more hydrophilic and have lower molecular weight than poorly ionizable components. Additionally, a discrepancy between the samples of terrestrial and marine origins was found, indicating that marine samples are better represented by ESI than terrestrial samples, which have an abundant portion of hydrophobic poorly ionizable material.
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| 8. |
- Patriarca, Claudia, et al.
(författare)
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Online HPLC-ESI-HRMS Method for the Analysis and Comparison of Different Dissolved Organic Matter Samples
- 2018
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 52:4, s. 2091-2099
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Tidskriftsartikel (refereegranskat)abstract
- Natural dissolved organic matter (DOM) is an ultracomplex mixture that is essential to global carbon cycling but is poorly understood because of its complexity. The most powerful tool for the DOM characterization is high-resolution mass spectrometry (HRMS) generally combined to direct infusion (DI) as sample introduction. Liquid chromatography (LC) represents a compelling alternative to DI; however, state-of-the-art techniques involve only offline LC-HRMS approaches, which have important logistical drawbacks that make DOM analysis more challenging. This study introduces a new method based on online coupling of liquid chromatography to high resolution mass spectrometry, able to overcome the disadvantages of usual approaches. It is characterized by high reproducibility (% Bray–Curtis dissimilarity among replicates ≈ 2.5%), and it reduces transient complexity and contaminant interferences, thus increasing the signal-to-noise ratio (S/N), leading to the identification of an overall larger number of formulas in the mixture. Moreover, the application of an in silico fractionation prior to the statistical analysis allows an easy, flexible, fast, and detailed comparison of DOM samples from a variety of sources with a single chromatographic run.
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