A mini-electrodialysis system for desalting small volume saline samples for Fourier transform ion cyclotron resonance mass spectrometry

An affordable, commercially available mini-electrodialysis (mini-ED) system has been evaluated for the efficient desalting of small volume samples of seawater before analysis by electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). Mini-ED FT-ICR mass spectra were compared with spectra for samples that were treated by C-18 solid phase extraction, a commonly used method for rapid sample preparation for this type of analysis. In this comparison, it is clear that mini-ED provides more representative molecular information, compared with C-18 isolation, and recovers the overwhelming majority of peaks from salt-free samples, indicating that it adequately represents the DOM that can be ionized and analyzed by ESI FT-ICR MS. The ED system produces a significant carbon blank. However, the substances contributing to this blank are not detectable by ESI FT-ICR MS. Based on these findings mini-ED is recommended as a promising method for the desalting of aqueous environmental samples before analysis by ESI FT-ICR MS.