High Molecular Weight Spectral Interferences in Mass Spectra of Dissolved Organic Matter

In this paper we investigate interferences that appear in molecular mass spectra from aquatic samples. The interferences are identified as doubly charged ions originating from high molecular weight material, which is especially abundant in terrestrial samples. The interferences could be incorrectly assigned to singly charged formulas with high aromaticity and heteroatom content, as the mass error from such formulas can be less than 1 ppm. We propose a strategy for filtering the interference peaks from mass lists based on the presence of their equivalent isotopologue peaks at mass defects of ∼0.5 Da.