title: Extension of the focusable mass range in distance-of-flight mass spectrometry with multiple detectors.
abstract: BACKGROUND
  Distance-of-flight mass spectrometry (DOFMS) is a velocity-based mass separation technique in which ions are spread across a spatially selective detector according to m/z. In this work, we investigate the practical mass range available for DOFMS with a finite-length detector.
  
  
  METHODS
  A glow-discharge DOFMS instrument has been constructed for the analysis of atomic ions. This instrument was modified to accommodate two spatially selective ion detectors, arranged co-linearly, along the mass-separation axis of the analyzer. With this geometry, each detector covers a different portion of the distance-of-flight spectrum and ions are detected simultaneously at the two detectors. The total flight distance covered by the two detectors is 106 mm and simulates DOF detection across a broad mass range.
  
  
  RESULTS
  DOFMS theory predicts that ions of all m/z values are focused at a single flight time, but at m/z-dependent flight distances. Therefore, ions that are detected across a wide portion of the DOF axis should all yield the same peak widths. With a focal-plane camera detector and a micro-channel plate/phosphor-screen detection assembly, we found simultaneous, uniform focus of (40)Ar(2)(+) and of (65)Cu(+) and (63)Cu(+) with the ions spread 82 mm across the DOF axis. This detection length, combined with the current instrument geometry, allows for a simultaneously detectable m/z value of 4:3 (high mass-to-low mass).
  
  
  CONCLUSIONS
  These results are the first experimental verification that constant-momentum acceleration (CMA)-DOFMS provides energy focus across an extended detection length. Evidence presented demonstrates that DOFMS is amenable to detection with (at least) a 100-mm detector surface. These results indicate that DOFMS is well suited for detection of broader mass ranges.
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Gundlach-Graham
authors.forename: Elise A
authors.initials: EA
authors.lastname: Dennis
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Ray
authors.forename: Christie G
authors.initials: CG
authors.lastname: Enke
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Carado
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Barinaga
authors.forename: David W
authors.initials: DW
authors.lastname: Koppenaal
authors.forename: Gary M
authors.initials: GM
authors.lastname: Hieftje