title: Study on the detection limits of a new argon gas cluster ion beam secondary ion mass spectrometry apparatus using lipid compound samples.
abstract: BACKGROUND
  Ar gas cluster ion beam secondary ion mass spectrometry (Ar-GCIB SIMS) has been developed as one of the most powerful tools used for analyzing complex biological materials because of its distinctively high secondary ion yield of large organic molecules. However, for the practical analysis of minor components in complex biological materials, the sensitivity of the technique is still insufficient.
  
  
  METHODS
  The detection limits of our original Ar-GCIB SIMS apparatus were investigated by measuring lipid compound samples in positive ion mode. The samples were mixtures of 1,2-distearoyl-sn-glycero-3-phosphocholine (C44 H88 NO8 P, DSPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (C40 H80 NO8 P, DPPC). The primary ions were accelerated with 10 keV and the mean cluster size was 1500. The secondary [M+H](+) ions emitted from the sample were analyzed using an orthogonal acceleration time-of-flight mass spectrometer (oa-TOF-MS). In addition, the isotope abundance ratio and the ratio of the [M+H](+) ion signal to the fragment ion signal acquired with Ar-GCIB SIMS were compared with those obtained with conventional Bi cluster SIMS.
  
  
  RESULTS
  Secondary [M+H](+) ions and some characteristic fragment ions were clearly observed with high quantitative accuracy in the mass spectra acquired with Ar-GCIB SIMS. The results were clearly better than those obtained with conventional Bi cluster SIMS.
  
  
  CONCLUSIONS
  The detection limit of Ar-GCIB SIMS was found to be below 0.1% and was much lower than that of conventional Bi cluster SIMS because of the high [M+H](+) ion yield and the low background. The results suggested that the new Ar-GCIB SIMS apparatus has the capability to acquire valuable information on complex biological materials.
authors.affiliation: Quantum Science and Engineering Center, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Fujii
authors.forename: Shunichirou
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Matsuda
authors.forename: Naoki
authors.initials: N
authors.lastname: Man
authors.forename: Toshio
authors.initials: T
authors.lastname: Seki
authors.forename: Takaaki
authors.initials: T
authors.lastname: Aoki
authors.forename: Jiro
authors.initials: J
authors.lastname: Matsuo
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000032:analysis / Q000737:chemistry; D001128:Argon / Q000737:chemistry*; D007477:Ions / Q000032:analysis / Q000737:chemistry; D057230:Limit of Detection; D008956:Models, Chemical; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods*
chemical_list: D007477:Ions; D015060:1,2-Dipalmitoylphosphatidylcholine; D001128:Argon