Definitive identification of choline in irradiated ethanolamine–water–methanol ice

Determine whether electron irradiation of layered ethanolamine–water–methanol ice produces choline or choline-like quaternary-ammonium species, using measurements capable of resolving the spectral overlap and matrix effects that prevent definitive identification from the available infrared data.

Background

The study observes infrared bands near 895 and 850 cm⁻¹ that are compatible with quaternary-ammonium or N-methylated species, and the residue’s ESI-MS mass-family distribution resembles that of a choline chloride reference. However, the same spectral regions contain overlapping contributions from other nitrogen- and oxygen-bearing products, including methylated ethanolamine derivatives and polyoxymethylene-related material.

The available ESI-MS measurements provide nominal mass-family patterns but no structural information or isolated diagnostic signal at the nominal choline-cation mass. Consequently, the experiments suggest but do not establish choline formation, leaving definitive identification as an unresolved analytical problem requiring more structurally diagnostic measurements.

References

While these observations are suggestive, definitive identification of choline cannot be made from the infrared spectra alone because of spectral overlap and matrix effects.

— Electron irradiation and temperature-programmed desorption of layered ethanolamine-water-methanol ices  (2609.20111 - Stoib et al., 17 Sep 2026) in Section 3.2, subsection “Irradiation studies”; see also Section 4, subsection “N/O-bearing complex residue components and methylation pathways,” and Section 6, Conclusions