title: Desorption of low-volatility compounds induced by dynamic friction between microdroplets and an ultrasonically vibrating blade.
abstract: Friction plays an important role in desorption and/or ionization of nonvolatile compounds in mass spectrometry, e.g., sonic spray, easy ambient sonic-spray ionization, solvent-assisted inlet ionization, desorption electrospray, etc. In our previous work, desorption of low molecular weight compounds induced by solid/solid dynamic friction was studied. The objective of this work was to investigate desorption of low-volatility compounds induced by liquid/solid friction. Water/methanol (1/1) microdroplets with ∼30 μm in diameter were generated by using a piezoelectric microdroplet generator. They were injected to analytes deposited on the flat surface of a blade vibrating ultrasonically with the frequency of 40 kHz. Neutral molecules desorbed from the blade were ionized by a helium dielectric barrier discharge (DBD), generating strong signals for samples including drugs, explosives, and insecticides. These signals were not detected when either the blade vibrator or the piezoelectric microdroplet generator was off. In contrast, for ionic compounds such as 1-butyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)imide, p-chlorobenzyl pyridinium chloride, and rhodamine B, strong ion signals were obtained when the vibrator and droplet generator were on, but DBD was off. Sub-nanogram limits of detection were attained for low-volatility compounds.
authors.affiliation: Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu 400-8511, Japan. hiraoka@yamanashi.ac.jp and Institute of Ion-Plasma and Laser Technologies, Dormon Yoli Street 33, Akademgorodok, Tashkent 100125, Uzbekistan.
authors.forename: D T
authors.initials: DT
authors.lastname: Usmanov
authors.affiliation: Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu 400-8511, Japan. hiraoka@yamanashi.ac.jp.
authors.forename: K
authors.initials: K
authors.lastname: Hiraoka
authors.affiliation: Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, 496 Izumi, Chikugo, Fukuoka 833-0041, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Wada
authors.affiliation: Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, 496 Izumi, Chikugo, Fukuoka 833-0041, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Morita
authors.affiliation: Plant Biophysics/Biochemistry Research Laboratory, Faculty of Agriculture, Ehime University, Matsuyama, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nonami