The application of electrospray ionization mass spectrometry (ESI MS) to the structural characterization of natural organic matter

This report describes the application of electrospray ionization (ESI) mass spectrometry to the structural characterization of soil organic material, a critical component of environmental processes and the global carbon cycle. Quadrupole time-of-flight (QqTOF) mass spectrometry provided a routine screening of aqueous ions in humic and fulvic acid mixtures and MS/MS capabilities for selected ions. Fourier transform ion cyclotron resonance (FT–ICR) mass spectrometry required longer analysis time but achieved resolving powers >80,000 and mass accuracies of <1 ppm, which allowed exact molecular formula determination for selected peaks. This technique represents a significant advance in the identification of compounds within humic substances.