Molecular Size-Selective Electrodialytic Desalters for Electrospray Ionization-Mass Spectrometry

Area of Science:

• Analytical Chemistry
• Biotechnology
• Separation Science

Background:

• Mass spectrometry (MS) detection is hindered by salts and buffer components.
• These substances cause signal suppression, adduct formation, and inlet contamination in MS.
• Selective removal of salts is crucial for sensitive and accurate MS analysis of biomolecules.

Purpose of the Study:

• To develop and evaluate a membrane-based electrodialytic desalter for retaining large charged molecules like proteins.
• To assess the device's efficiency in removing salts prior to MS detection.
• To investigate the energetics and optimal voltage profiles for salt removal and conversion.

Main Methods:

• A planar electrodialysis device was designed using dialysis membranes (DMs) and ion exchange membranes (IEMs).
• The device employs an electric field across four pairs of electrodes to remove ions.
• The study investigated two scenarios: general ion removal and conversion of salts (e.g., ammonium acetate to acetic acid).

Main Results:

• The device selectively removed buffer/salt constituents while retaining proteins.
• Recovery of bovine serum albumin ranged from 67% to 96%.
• The device processed 200 mM ammonium acetate at 0.25 mL/min, converting it to acetic acid with dispersion volumes under 200 μL².

Conclusions:

• The membrane-based electrodialytic desalter effectively removes salts, preserving larger biomolecules for MS analysis.
• The device shows potential for coupling with liquid chromatography for enhanced MS workflows.
• Optimized voltage profiles and understanding electroosmotic flow are key for efficient desalting.