Fragmentation studies for the structural characterization of marine dissolved organic matter

Abstract

High-resolution tandem mass spectrometry by collision-induced dissociation with a linear ion trap-Orbitrap has been performed on marine dissolved organic matter (DOM). Product ion spectra of selected precursor ions (m/z 359-375) have been acquired to obtain structural information, after method development. To evaluate the performance of the method, the Suwannee River fulvic acid (SRFA) reference standard was also analyzed. By reconstructing the individual product ion spectrum of marine DOM, several fragments were assigned to the different precursor ions indicating the presence of carboxyl, hydroxyl, lactones, quinones, esters, and structures more similar to lignin-degraded molecules. On the basis of these findings, coastal marine DOM molecules, although structurally homogeneous, might be more rich in diversity of functional groups than previously described.

Molecular Signals of Heterogeneous Terrestrial Environments Identified in Dissolved Organic Matter: A Comparative Analysis of Orbitrap and Ion Cyclotron Resonance Mass Spectrometers

“…However, Orbitrap mass analyzers have a ∼10-fold lower mass resolution that limits separation of peaks in the higher mass range ( Supplementary Table S1). Even so, Orbitrap instruments have been successfully applied for characterizing complex natural organic materials ( Supplementary Table S2), including DOM (Pomerantz et al, 2011;Cortés-Francisco and Caixach, 2015;Hawkes et al, 2016), humic and fulvic acids (Galindo and Del Nero, 2015;Nebbioso and Piccolo, 2015), petroleum and bio-oilrelated material (Pomerantz et al, 2011;Zhurov et al, 2013;Rowland et al, 2014;Staš et al, 2015), and extraterrestrial organic materials (Danger et al, 2013;Smith et al, 2014), yet it remains unclear how comparable the results of both instrument types are. Addressing this question is even more pivotal when aiming to compare trends in larger-scale DOM sample sets achieved on different instruments (Swenson et al, 2014).…”

Development and Application of High-Precision Algorithm for Non-Target Identification of Organohalogens Based on Ultrahigh-Resolution Mass Spectrometry

“…The parent peaks with relative abundance (RA) ≥ 0.5% were only considered in the analysis, where the parent peak was defined by the mono-isotopic peak for the most abundant isotopologue (in terms of RA) among the multi-isotopic peaks with same halogenated chemical formula but different isotopic composition. Formulae were assigned to the peaks with signal to noise ratio ≥4 under the following conditions: 0.3≤X/C≤ 2.25 (where X = H+ Cl+ Br), 0< O/C ≤ 1.15 (0≤O when C≥5), double-bond equivalent (DBE) ≥0, 1≤ 12 C≤50, 0≤ 13 C≤ 2, 0≤ 18 O≤ 1, N≤ 5, 32 S≤ 3, 0≤ 34 S≤ 1, and P ≤ 1, 35 Cl≤ 5, 37 Cl≤ 5, 79 Br≤ 5, 81 Br≤ 5. Some molecular characteristics including O/C, H/C, X/C, modified aromaticity index (AImod), DBE, DBE/C, nominal oxidation state of carbon (NOSC) were also calculated in the algorithms.…”

“…Notably, due to the close mass differences between 32 S and 34 S (Δm/z=1.995796), 35 Cl and 37 Cl (Δm/z=1.997050), and 79 Br and 81 Br (Δm/z=1.997953), multi-isotopic peaks with the same number of heavy isotope are generally overlapped in the UHR-MS spectra. For example, the 37 Cl-isotopic peak of C9H18O6 37 Cl1 79 Br1 will be completely overlapped by the 81 Br-isotopic peak of C9H18O6 35 Cl1 81 Br1 due to its higher abundance compared to 13 C9H18O6 37 Cl1 79 Br1.…”

Development and Application of High-Precision Algorithm for Non-Target Identification of Organohalogens Based on Ultrahigh-Resolution Mass Spectrometry

“…The parent peaks with relative abundance (RA) ≥ 0.5% were only considered in the analysis, where the parent peak was defined by the mono-isotopic peak for the most abundant isotopologue (in terms of RA) among the multi-isotopic peaks with same halogenated chemical formula but different isotopic composition. Formulae were assigned to the peaks with signal to noise ratio ≥4 under the following conditions: 0.3≤X/C≤ 2.25 (where X = H+ Cl+ Br), 0< O/C ≤ 1.15 (0≤O when C≥5), double-bond equivalent (DBE) ≥0, 1≤ 12 C≤50, 0≤ 13 C≤ 2, 0≤ 18 O≤ 1, N≤ 5, 32 S≤ 3, 0≤ 34 S≤ 1, and P ≤ 1, 35 Cl≤ 5, 37 Cl≤ 5, 79 Br≤ 5, 81 Br≤ 5. Some molecular characteristics including O/C, H/C, X/C, modified aromaticity index (AImod), DBE, DBE/C, nominal oxidation state of carbon (NOSC) were also calculated in the algorithms.…”

“…To detect organohalogens using mass spectrometry, researchers typically employ isotopic pattern representing unique peak combinations of multiple isotopes with different masses and natural abundances (Meusel et al, 2016). Given the high natural abundance of Cl (75.78% for 37 Cl and 24.22% for 35 Cl) and Br isotopologues (50.69% for 79 Br and 49.31% for 81 Br), the isotopic pattern of Cl and Br (e.g. chlorinated X-DBPs [Cl-DBPs], brominated X-DBPs [Br-DBPs], and Cl-and Br-containing X-DBPs [Cl-Br-DBPs]) is a distinctive signal in organohalogens detection with high levels of confidence.…”