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SIMS21, Poland 2017 - Yukio Fujiwara abstract

Yukio Fujiwara oral presentation (PB1-Mon1-1-2)

A new primary ion beam source using vacuum electrospray of protic ionic liquids

Yukio Fujiwara, Naoaki Saito

National Institute of Advanced Industrial Science and Technology (AIST), Umezono, 305-8568 Tsukuba, Japan

Ionic liquids can be divided into two broad categories: aprotic ionic liquids and protic ionic liquids. Protic ionic liquids (PILs) are promising materials for massive-cluster ion beams used in TOF-SIMS. This is because a molecule of a PIL has a mobile proton, so that its beam can enhance the formation of protonated molecules.[1]

We have developed a new primary ion beam source using vacuum electrospray, and then demonstrated that a primary ion beam of a PIL, diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]), was effective in protonating arginine; however, it was not effective in protonating polyethylene glycol.[2] The results obtained were explained by considering gas-phase basicities (BAs) and proton affinities (PAs) of analytes and [dema][TfO] constituents.[2]

A wide variety of PILs has been commercially available. In view of GBs and PAs, propylammonium nitrate ([C3H7NH3][NO3]) appears to be one of the most promising candidates for application to SIMS.

For this reason, we have investigated the usefulness of [C3H7NH3][NO3] as a primary ion beam in TOF-SIMS. We have analyzed amino acids, angiotensin II and polyethylene glycol using a primary ion beam of [C3H7NH3][NO3]. The experimental results showed that the primary beam of [C3H7NH3][NO3] successfully generated protonated molecular ions of all the analytes tested. Consequently, [C3H7NH3][NO3] proved to be more useful than [dema][TfO] in terms of TOF-SIMS analysis.

[1] Y. Fujiwara, N. Saito, Appl. Phys. Express 2015, 8, 076601.

[2] Y. Fujiwara, N. Saito, Rapid Commun. Mass Spectrom. 2016, 30, 239-249.