title: Electrospray droplet impact secondary ion mass spectrometry using a vacuum electrospray source.
abstract: BACKGROUND
  In electrospray droplet impact (EDI) developed in our laboratory, an atmospheric pressure electrospray source has been used. To increase the ion beam intensity and reduce the evacuation load, a vacuum electrospray cluster ion source using a silica capillary was developed.
  
  
  METHODS
  A silica capillary with a tip inner diameter of 8 µm was used for vacuum electrospray using aqueous 10% methanol. To stabilize the flow rate of the liquid for nano-electrospray, a home-made constant pressure liquid pump was also developed.
  
  
  RESULTS
  By using the silica tip nano-electrospray emitter and a constant pressure pump, stable electrospray with flow rate of 22 nL/min was realized without using any heating system such as laser irradiation. Comparative study of mass spectra obtained by atmospheric pressure EDI (A-EDI) and vacuum EDI (V-EDI) was made for various samples such as thermometer molecule, peptide, polystyrene, Alq(3), NPD, C(60), indium, and SiO(2). V-EDI showed slightly milder ionization than A-EDI.
  
  
  CONCLUSIONS
  Because V-EDI gave higher target current (5-10 nA) than A-EDI (a few nA at most), V-EDI secondary ion mass spectrometry (SIMS) would be a useful technique for the surface and interface analysis.
authors.affiliation: Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu, 400-8511, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Takaishi
authors.affiliation: Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu, 400-8511, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Sakai
authors.affiliation: Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu, 400-8511, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hiraoka
authors.affiliation: Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 496 Izumi, 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 (NARO), 496 Izumi, 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, 790-8566, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nakashima
authors.affiliation: Plant Biophysics/Biochemistry Research Laboratory, Faculty of Agriculture, Ehime University, Matsuyama, 790-8566, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nonami
mesh_terms: D008956:Models, Chemical; D012822:Silicon Dioxide; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation* / Q000379:methods*; D014618:Vacuum
chemical_list: D012822:Silicon Dioxide