title: Enhancement of laser desorption ionization mass spectrometric signals of cesium iodide by elemental sulfur.
abstract: BACKGROUND
  The utility of elemental sulfur as a matrix for inorganic salts such as CsI, AgI, and KI was investigated because the conventional matrices deployed to generate gaseous ions from organic compounds, upon irradiation with a laser beam, are not suitable for inorganic salts.
  
  
  METHODS
  Sulfur and inorganic salts were admixed and irradiated with a 337-nm UV laser. Laser desorption ionization (LDI) mass spectra were recorded in both positive and negative ion mode on a time-of-flight mass spectrometer.
  
  
  RESULTS
  The positive ion laser desorption ionization mass spectrum of CsI showed peaks at m/z 133, 393, etc. for [(CsI)(n)Cs](+) ions. Similarly, negative ion spectra showed peaks at m/z 387, 647, etc. for [(CsI)(n)I](-) ions. However, for n >2 ion clusters, the intensities of peaks were negligibly small in both ionization modes. In contrast, spectra recorded from CsI admixed with elemental sulfur showed peaks up to n = 13 for (CsI)(n)Cs(+), and n = 9 for (CsI)(n)I(-). A similar enhancement of ion abundances by sulfur was observed for the cluster ions generated from KI and AgI.
  
  
  CONCLUSIONS
  The dramatic increase in intensities of the higher-mass CsI cluster peaks suggests that sulfur acts as a laser-absorbing matrix for inorganic salts far superior to conventional matrices such as 2,5-dihydroxybenzoic acid and α-cyano-4-hydroxycinnamic acid.
authors.affiliation: Center for Mass Spectrometry, Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kruegel
authors.forename: Julius
authors.initials: J
authors.lastname: Pavlov
authors.forename: Athula B
authors.initials: AB
authors.lastname: Attygalle
mesh_terms: D002586:Cesium / Q000737:chemistry*; D007454:Iodides / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013455:Sulfur / Q000737:chemistry*
chemical_list: D007454:Iodides; D007477:Ions; D002586:Cesium; D013455:Sulfur; C040050:cesium iodide