Total mass difference statistics algorithm: A new approach to identification of high-mass building blocks in electrospray ionization fourier transform ion cyclotron mass spectrometry data of natural organic matter

Erast V. Kunenkov, Alexey S. Kononikhin, Irina V. Perminova, Norbert Hertkorn, Andras Gaspar, Philippe Schmitt-Kopplin, Igor A. Popov, Andrew V. Garmash, Evgeniy N. Nikolaev

Research output: Contribution to journalArticlepeer-review

60 Citations (Scopus)

Abstract

The ultrahigh-resolution Fourier transform ion cyclotron resonance (FTICR) mass spectrum of natural organic matter (NOM) contains several thousand peaks with dozens of molecules matching the same nominal mass. Such a complexity poses a significant challenge for automatic data interpretation, in which the most difficult task is molecular formula assignment, especially in the case of heavy and/or multielement ions. In this study, a new universal algorithm for automatic treatment of FTICR mass spectra of NOM and humic substances based on total mass difference statistics (TMDS) has been developed and implemented. The algorithm enables a blind search for unknown building blocks (instead of a priori known ones) by revealing repetitive patterns present in spectra. In this respect, it differs from all previously developed approaches. This algorithm was implemented in designing FIRAN-software for fully automated analysis of mass data with high peak density. The specific feature of FIRAN is its ability to assign formulas to heavy and/or multielement molecules using "virtual elements" approach. To verify the approach, it was used for processing mass spectra of sodium polystyrene sulfonate (PSS, Mw ) 2200 Da) and polymethacrylate (PMA, Mw ) 3290 Da) which produce heavy multielement and multiply-charged ions. Application of TMDS identified unambiguously monomers present in the polymers consistent with their structure: C8H 7SO3Na for PSS and C4H6O2 for PMA. It also allowed unambiguous formula assignment to all multiply-charged peaks including the heaviest peak in PMA spectrum at mass 4025.6625 with charge state 6- (mass bias -0.33 ppm). Application of the TMDS-algorithm to processing data on the Suwannee River FA has proven its unique capacities in analysis of spectra with high peak density: it has not only identified the known small building blocks in the structure of FA such as CH2, H2, C2H2O, O but the heavier unit at 154.027 amu. The latter was identified for the first time and assigned a formula C7H6O4 consistent with the structure of dihydroxyl-benzoic acids. The presence of these compounds in the structure of FA has so far been numerically suggested but never proven directly. It was concluded that application of the TMDS-algorithm opens new horizons in unfolding molecular complexity of NOM and other natural products.

Original languageEnglish
Pages (from-to)10106-10115
Number of pages10
JournalAnalytical Chemistry
Volume81
Issue number24
DOIs
Publication statusPublished - 15 Dec 2009
Externally publishedYes

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