title: Scanning probe electrospray ionization for ambient mass spectrometry.
abstract: BACKGROUND
  Ambient sampling and ionization techniques have been attracting attention in imaging mass spectrometry because they offer the advantage of rapid testing. We have developed a method which exploits the fluid motion of charged solvents for both local sampling and ionization with a single vibrating capillary probe.
  
  
  METHODS
  The capillary probe was used to supply solvents in order to form a liquid bridge between the probe and a sample surface. A bias voltage was applied to the solvents to generate electrospray ionization (ESI). The probe was also vibrated by either an ultrasonic transducer fixed at the back of the sample (contact-mode) or spontaneous vibration of probe itself (tapping-mode). The ions generated by ESI were detected by a triple quadrupole mass spectrometer.
  
  
  RESULTS
  Sampling of the specimens at the liquid bridge and ESI of the dissolved solutions both occurred around the probe apex. The sampling and ionization co-existed in contact-mode, while they were explicitly separated in the tapping-mode. The one-dimensional mapping of solid samples such as protein films and tissue sections was demonstrated. The results indicated that there was little cross-contamination during the operation.
  
  
  CONCLUSIONS
  The method, named scanning probe electrospray ionization (SPESI), promises to be a simple and unique approach toward direct sampling and ionization methodology.
authors.affiliation: Frontier Research Center, Canon Inc., 30-2 Shimomaruko 3-chome, Ohta-ku, Tokyo, 146-8501, Japan. otsuka.yoichi@canon.co.jp
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Otsuka
authors.forename: Sayuri
authors.initials: S
authors.lastname: Shide
authors.forename: Junpei
authors.initials: J
authors.lastname: Naito
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kyogaku
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hashimoto
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Arakawa
mesh_terms: D000818:Animals; D002417:Cattle; D004867:Equipment Design; D006801:Humans; D007328:Insulin / Q000737:chemistry; D051379:Mice; D010179:Pancreas / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013048:Specimen Handling; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation* / Q000379:methods
chemical_list: D007328:Insulin; D012710:Serum Albumin, Bovine