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Time‐of‐flight secondary ion mass spectrometry using a new primary ion beam generated by vacuum electrospray of a protic ionic liquid, propylammonium nitrate
Author(s) -
Fujiwara Yukio,
Saito Naoaki
Publication year - 2017
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7960
Subject(s) - chemistry , protonation , ion , deprotonation , molecule , secondary ion mass spectrometry , mass spectrometry , electrospray ionization , reflectron , inorganic chemistry , analytical chemistry (journal) , time of flight mass spectrometry , ionization , organic chemistry , chromatography
Rationale Protic ionic liquids have the potential to be useful materials for primary ion beams in terms of protonation, since they have active protons. Selecting protic ionic liquids suitable for primary ion beams is of great importance to increase molecular secondary ion yields. Propylammonium nitrate ([C 3 H 7 NH 3 ][NO 3 ]) seems promising in view of its proton affinity. It is likely that [C 3 H 7 NH 3 ] + cations can act as proton donors, and [NO 3 ] − anions can work as proton acceptors. Methods Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) experiments have been performed to verify the usefulness of [C 3 H 7 NH 3 ][NO 3 ]. A primary propylammonium nitrate cluster ion beam was generated by vacuum electrospray, and then used to analyze amino acids (arginine, glutamic acid, aspartic acid), angiotensin II and polyethylene glycol. Positive and negative secondary ion mass spectra were obtained to study both protonation and deprotonation. Results The propylammonium nitrate cluster ion beam successfully generated protonated molecules [M + H] + of all the analytes in positive ion mode. The primary ion beam also generated deprotonated molecules [M − H] − of glutamic acid, aspartic acid and angiotensin II in negative ion mode. Additionally, adduct ions related to [C 3 H 7 NH 3 ][NO 3 ] were detected in the case of arginine and polyethylene glycol. Conclusions The TOF‐SIMS experiments confirmed that the propylammonium nitrate cluster ion beam was useful in generating molecular secondary ions, demonstrating that it is well suited for a primary ion beam in TOF‐SIMS.