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High-Field FTICR-MS Data Evaluation of Natural Organic Matter: Are CHON5S2 Molecular Class Formulas Assigned to 13C Isotopic m/z and in Reality CHO Components?
journal contribution
posted on 2015-10-06, 00:00 authored by Peter Herzsprung, Wolf v. Tümpling, Norbert Hertkorn, Mourad Harir, Kurt Friese, Philippe Schmitt-KopplinThe
analysis of dissolved organic matter (DOM) using high-field
Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS)
poses challenges in molecular formula assignment. The consideration
of 13C isotopes provides new insights into the consistent
elemental formula solutions. Modern software helps to overcome misinterpretation,
but false assignments of molecular classes to mass peaks have rarely
been elucidated until now. It will be demonstrated that this can be
important with formula assignments comprising exactly five nitrogen
and two sulfur atoms in DOM data sets: the molecular class CHON5S2. The existence of such components in DOM under
tripeptide Met–His–Cys formed with the formula C14H23O4N5S2 cannot
be excluded; however, components containing 5 N and 2 S should be
suspected to not be highly abundant. The true elemental compositions
of such unusual “N5S2 moieties”
were calculated using Suwannee River fulvic acid (SRFA) data from
the literature and one data set from acidic pit lake pore water. The
replacement of a H3N5S2 moiety with
a 13C112C5O4 moiety explained more than 95% of the questionable “N5S2 moieties”. This finding was proved by
calculation of δ13C‰ values from relative
peak intensities.
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acidic pit lake pore waterDOM data setsclass CHON 5Sion cyclotron resonance mass spectrometryH 3N moiety2 S13 C 112C moietyNatural Organic Mattercomponentformula C 14HSuwannee River fulvic acid13 C isotopesformula assignmentModern softwareformula solutions5 Nmoietieformula assignmentsCHON 5S Molecular Class Formulas Assignedmass peakssulfur atomsSRFApeak intensities
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