Optimization of ionization conditions for analysis of humic substances from natural waters using Electrospray Ionization Fourier Transform Ion Cyclotron Resonance mass spectrometry (ESI FTICR MS)

An approach to optimizing conditions of acquiring Electrospray Ionization Fourier Transform Ion Cyclotron Resonance mass spectra (ESI FTICR MS) was suggested. This method was employed to study the influence of cone voltage and the composition of the solution on peak intensity in ESI FTICR mass spectra of natural water humic substances. A presence of water in methanol solution was shown to reduce signal intensity significantly. The highest integral intensity of peaks selected was reached on 110 mg/l sample solution in acetonitrile and cone voltage 3.0 kV. The number of peaks to which molecular formulas were assigned, including doubly-charged peaks, was increased using these conditions.