title: Detection of oligonucleotides by external injection into an ion trap storage/reflection time-of-flight device.
abstract: The detection of oligonucleotides has been studied using external injection of Matrix-assisted laser desorption/ionization (MALDI) produced ions into a quadrupole ion trap storage device. The ions stored in the trap are then detected by pulsed DC injection into a reflection time-of-flight mass spectrometer. It is shown that by using a low acceleration voltage from the probe tip and external injection into the trap that 3-mers to 9-mers can be stored for 20-50 ms and detected as intact ions. In comparison, direct MALDI inside the trap resulted in extensive fragmentation as a function of storage time. Using the external injection with a He buffer gas in the trap yields a resolution of 250-400 in the ion trap storage/reflectron time-of-flight mass spectrometer. The resolution can be further enhanced to 400-800 using a bipolar extraction method. In addition, the trapping efficiency for the injection of externally produced ions into the trap can be enhanced using a dynamic trapping method. The MALDI mass spectra produced by this methodology result in excellent signal-to-noise ratio due to the capabilities of the trap for eliminating low mass matrix background from the spectra.
authors.affiliation: Department of Chemistry, University of Michigan, Ann Arbor 48109-1055, USA.
authors.forename: L
authors.initials: L
authors.lastname: He
authors.forename: Y H
authors.initials: YH
authors.lastname: Liu
authors.forename: Y
authors.initials: Y
authors.lastname: Zhu
authors.forename: D M
authors.initials: DM
authors.lastname: Lubman
mesh_terms: D001330:Electronic Data Processing; D008401:Gas Chromatography-Mass Spectrometry; D009841:Oligonucleotides / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D009841:Oligonucleotides