High-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of Humic and Fulvic Acids by Laser Desorption/Ionization and Electrospray Ionization

Abstract

High-field (9.4 T) Fourier transform ion cyclotron resonance (FT-ICR) mass spectra of standard Suwannee River humic and fulvic acids have been obtained by use of laser desorption (LDI) and electrospray (ESI) ionization. The LDI FT-ICR mass spectrum was similar to those observed previously, with ions at essentially every nominal value, 200 ≤ m/z ≤ 800. In contrast, the ESI FT-ICR mass spectrum, although still containing ions at most values in the 200 ≤ m/z ≤ 800 range, was dominated by a relatively few prominent species. ESI FT-ICR mass spectra of standard humic and fulvic acid isolates were similar. Although many ionic species appeared in both fulvic acid and humic acid ESI FT-ICR mass spectra, the fulvic acid mass spectrum contained more highly charged species. Subfractions of the fulvic acid mixture isolated by an HPLC procedure yielded similar mass spectra. The stability of high-mass ions produced by ESI combined with the high-mass resolution capability of FT-ICR MS allow for precise determination of molecular masses, from which molecular formulas may be obtained by mass alone. Future two-dimensional FT-ICR MS2 determinations of humic and fulvic acid structures should be feasible by use of collisionally induced and multiple-photon dissociation techniques.

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

“…Laser desorption ionization (LDI) and matrix assisted laser desorption/ionization (MALDI), two other soft ionization methods, are also used for NOM characterization. However, LDI might generate excessive fragmentation of NOM during the ionization process because it is a relatively energetic ionization method [14,15]. MALDI, with the addition of external matrices, can facilitate energy dispersion and enhance sample ionization, so this method tends to generate intact molecular ions with minimal or no fragmentation [16,17].…”

Impact of instrument and experiment parameters on reproducibility of ultrahigh resolution ESI FT-ICR mass spectra of natural organic matter

“…To date, most ESI FT-ICR MS analyses of DOM have addressed analytical challenges associated either with sample preparation and ion production, or with data analysis and interpretation. Researchers have made important contributions in these areas by optimizing protocols for DOM extraction and concentration (Kim et al, 2003;Koprivnjak et al, 2006;Dittmar et al, 2008;Morales-Cid et al, 2009), chromatographic pre-separation (Fievre et al, 1997;Koch et al, 2008;Reemtsma et al, 2008;Stenson, 2008;Gaspar et al, 2009), and ESI direct infusion (Brown and Rice, 2000;Kujawinski et al, 2002;Stenson et al, 2003;. Major advances have also been made for elemental formula assignments (Koch et al, 2005;Kujawinski and Behn, 2006;Koch et al, 2007;Kunenkov et al, 2009), graphical andcompositional analysis (Kim et al, 2003;Stenson et al, 2003;Wu et al, 2004;Koch and Dittmar, 2006), and multivariate statistical analysis (Koch et al, 2005;Koch et al, 2008;Rossello-Mora et al, 2008;Gougeon et al, 2009;Kujawinski et al, 2009).…”

Analytical Pyrolysis and Soft‐Ionization Mass Spectrometry

“…Innovative soft ionization techniques such as liquid injection fi eld desorption ionization (LIFDI) combined with MS (Linden, 2001(Linden, , 2002(Linden, , 2004Qian et al, 2004 ;Schaub et al, 2004Schaub et al, , 2005Rodgers et al, 2005 ;Fu et al, 2006a,b ;Gross et al, 2006 ), as well as the ultrahighresolution Fourier transform -ion cyclotron resonance mass spectrometry (FT -ICR MS) (e.g., Fievre et al, 1997 ;Marshall, 2000 ;Qian et al, 2001 ;Kujawinski et al, 2002 ;Llewelyn et al, 2002 ;Stenson et al, 2002Stenson et al, , 2003Fard et al, 2003 ), were recently introduced to applied environmental chemistry. These technical innovations will be described briefl y, and a few examples of applications will be given to demonstrate the tremendous potential to disclose composition, structure, and functions of nonliving organic matter.…”