Characterization of polyethylenimine by electrospray ionization and matrix-assisted laser desorption/ionization

Abstract

Branched polyethylenimines (PEIs) with lower average molecular weights (600, 1200 and 1800 Da) have been studied by Electrospray Ionization (ESI) and Matrix-Assisted Laser Desorption/Ionization (MALDI) mass spectrometry. In both, ESI and MALDI mass spectra, the main distribution arises from protonated PEI oligomers with NH(2) end groups, [PEI + H](+), which are observed at m/z 43n + 18. A trace of sodium contamination in the PEI samples results in the presence of a series that appears at m/z 43n + 40 [PEI + Na](+). However, only the MALDI mass spectra show a [PEI + K](+) series at m/z 43n + 56, because of matrix contamination with potassium, and a series generated by condensation of the matrix with PEI at m/z 43n + 30. Collisionally activated dissociation tandem mass spectrometry (CAD (MS/MS)) of protonated PEI oligomers is shown to yield three fragment ion series b(n), cn″ and K(n). The experiments have demonstrated the capabilities of these mass spectrometry techniques, along with CAD MS/MS to detect and characterize such polar synthetic polymers.

Strong ionic interactions in noncovalent complexes between poly(ethylene imine), a cationic electrolyte, and Cibacron Blue, a nucleotide mimic – implications for oligonucleotide vectors

“…Complexes containing at least one –SO 3 H group (A* 6 and B* 6 ) mainly dissociate within the PEI segment by losses of (C 2 H 4 NH) n and H 2 N(C 2 H 4 N) n H units (Fig. A and B), which is the typical dissociation pattern of protonated PEI oligomers . Fragments containing the CB unit are also observed in the m / z 408–560 region; likely structures for these fragments, which originate from bond cleavages in CB's triazine ring, and for dehydrated CB are given in Fig.…”

“…Additionally, PEI423 might be more branched than PEI600; branching increases the number of primary amine groups in PEI, which can be eliminated in form of ammonia upon cyclization. Most ions appearing in the low‐mass end of the ESI mass spectra ( m / z < ~400 for PEI600 and < ~240 for PEI423) are attributed to fragments formed during ESI–MS analysis …”

“…Most ions appearing in the low-mass end of the ESI mass spectra (m/z <~400 for PEI600 and <~240 for PEI423) are attributed to fragments formed during ESI-MS analysis. [54] The polysulfonated dye CB (Scheme 1) was also analyzed in both positive and negative ion mode by ESI-QIT mass spectrometry. CB does not form abundant positively charged ions; however, in negative ion ESI mode, intense monoanions of variously sodiated CB species and their fragment ions are observed, cf.…”

“…10A and 10B), which is the typical dissociation pattern of protonated PEI oligomers. [54] Fragments containing the CB unit are also observed in the m/z 408-560 region; likely structures for these fragments, which originate from bond cleavages in CB's triazine ring, and for dehydrated CB are given in Fig. 11.…”

A novel solventless coating method to graft low-molecular weight polyethyleneimine on silica fine powders

“…(a)], indicating a low molecular weight for the synthesized polymer, in agreement with the results obtained by SLS. Slight discrepancies on the absolute mass estimated using different characterization techniques are typical for such a low‐molecular weight polymers, shifting the molecular weight distribution to lower masses for MALDI‐ToF analysis . The maximum peak intensity was centered at 132–304 Da, corresponding to 3 (129 Da)−7 (301 Da) repeating units (CH 2 CH 2 NH) in the protonated PEI molecule.…”