Exact Masses and Chemical Formulas of Individual Suwannee River Fulvic Acids from Ultrahigh Resolution Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectra

Abstract

Molecular formulas have been assigned for 4626 individual Suwannee River fulvic acids based on accurate mass measurements from ions generated by electrospray ionization and observed by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). Formula assignments were possible because of the mass accuracy of FTICR MS at high field (9.4 T) and the regular mass spacing patterns found in fulvic acid mixtures. Sorting the 4626 individually observed ions according to Kendrick mass defect and nominal mass series (z* score) revealed that all could be assigned to 1 of 266 distinct homologous series that differ in oxygen content and double bond equivalence. Tandem mass spectrometry based on infrared multiphoton dissociation identified labile fragments of fulvic acid molecules, whose chemical formulas led to plausible structures consistent with degraded lignin as a source of Suwannee River fulvic acids.

Interactive van Krevelen diagrams – Advanced visualisation of mass spectrometry data of complex mixtures

“…With the mass accuracy of FTICR MS spectra in parts‐per‐billion,22, 23 routine and confident assignment of thousands of unique chemical formulae to individual peaks is now increasingly possible. The generation of this volume of data represents a significant challenge in terms of data visualisation, interrogation, and interpretation that has not been addressed so far.…”

Characterization of unknown iodinated disinfection byproducts during chlorination/chloramination using ultrahigh resolution mass spectrometry

“…The z* (Eq. (1)) value has been shown to be a useful parameter for presorting homologous series of fulvic acids (Hsu et al, 1992;Stenson et al, 2003;Reemtsma and These, 2005). In Eq.…”

“…Recently, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been successfully used to characterize the previously unknown Cl-DBPs and Br-DBPs (Zhang et al, 2012a;Zhang et al, 2012b;Lavonen et al, 2013;Zhang et al, 2014). The ultrahigh resolution and mass accuracy of FT-ICR MS combined with electrospray ionization (ESI) allows the determination of unambiguous and exact molecular formulas (Stenson et al, 2003;Kim et al, 2006aKim et al, , 2006bHertkorn et al, 2008). It is thus anticipated that the ESI FT-ICR MS method could also be suitable for identifying the molecular formulas of unknown I-DBPs.…”

Comprehensive characterization of natural organic matter by MALDI- and ESI-Fourier transform ion cyclotron resonance mass spectrometry

“…For visually graphic displays of the mass spectral data, the following parameters were calculated according to the previous reports: H/C ratio and O/C ratio, parameters for constructing Van Krevelen diagram [19]; Kendrick mass (KM) and Kendrick mass defect (KMD) for the purpose of identifying CH 2 -, CO 2 -, O-, CO-, H 2 O-, and H 2 -homologous molecular formulas series [7,20]; the modified aromaticity index (AI_mod) was calculated to estimate the fraction of aromatic and condensed aromatic structures [9,18]; the nominal oxidation state of carbon (NOSC) was calculated from the formulas to indirectly show the polarity of NOM constituents detected by FT-ICR-MS [9].…”

“…As a result, the extent of molecular information about NOM is largely restricted. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), due to its ultrahigh resolution and mass accuracy, can provide molecular elemental information about NOM without chromatographic separation [5,6], and has been used for accurate characterization of NOM [7][8][9]. Electrospray ionization (ESI) is the most commonly used ionization method for FT-ICR-MS characterization of NOM because it is one of the softest ionization methods and can be easily coupled with FT-ICR-MS [10,11].…”