Factors Affecting the Sampling of Poly(ethylenimines) by Electrohydrodynamic Mass Spectrometry

摘要

The effects of polymer structure and solution chemistry on sampling by electrohydrodynamic (EH) mass spectrometry were studied by using poly(ethylenimines) (PEIs). In contrast with results for poly(ethylene glycols), number average molecular weights (Mn) calculated from desorption ionization mass spectra of PEIs are generally too low, with the discrepancy becoming greater with increasing molecular weight. The effects of adding acid and transition-metal ions indicate that sampling bias in EH mass spectrometry is in part due to strong solvent-ion interactions resulting from poor shielding of charge sites in multiply charged adducts, with a contribution from hydrogen bonding interactions between polymer and solvent. Increases in apparent Mn when PEIs were sampled from mixed glycerol/water matrices result from changes in hydrogen bonding, ion pairing, and/or mass transport.