An ultrahigh-resolution mass spectrometry index to estimate natural organic matter lability

• Published in: Rapid communications in mass spectrometry 2015-12, Vol.29 (24), p.2385-2401
• Main Authors: D'Andrilli, Juliana, Cooper, William T., Foreman, Christine M., Marshall, Alan G.
• Format: Article
• Language: English
• Subjects: Antarctic Regions; Boundaries; Cartridges; Complex Mixtures - analysis; Complex Mixtures - chemistry; Constituents; Estimates; Extraction; Fresh Water - chemistry; Ionization; Ions; Magnetic fields; Mass spectrometry; Scientific imaging; Seawater - chemistry; Spectrometry, Mass, Electrospray Ionization - methods; Spectroscopy, Fourier Transform Infrared - methods
• ISSN: 0951-4198; 1097-0231
• DOI: 10.1002/rcm.7400

Rationale Determining the chemical constituents of natural organic matter (NOM) by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICRMS) remains the ultimate measure for probing its source material, evolution, and transport; however, lability and the fate of organic matter (OM) in the environment remain controversial. FTICRMS‐derived elemental compositions are presented in this study to validate a new interpretative method to determine the extent of NOM lability from various environments. Methods FTICRMS data collected over the last decade from the same 9.4 tesla instrument using negative electrospray ionization at the National High Magnetic Field Laboratory in Tallahassee, Florida, was used to validate the application of a NOM lability index. Solid‐phase extraction cartridges were used to isolate the NOM prior to FTICRMS; mass spectral peaks were calibrated internally by commonly identified NOM homologous series, and molecular formulae were determined for NOM composition and lability analysis. Results A molecular lability boundary (MLB) was developed from the FTICRMS molecular data, visualized from van Krevelen diagrams, dividing the data into more and less labile constituents. NOM constituents above the MLB at H/C ≥1.5 correspond to more labile material, whereas NOM constituents below the MLB, H/C  marine > freshwater. Applying the MLB is useful not only for individual NOM FTICRMS studies, but also provides a lability threshold to compare and contrast molecular data with other FTICRMS instruments that survey NOM from around the world. Copyright © 2015 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd.