Laser desorption Fourier transform ion cyclotron resonance (LD/FT/ICR) mass spectrometry for high mass ions

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7015762

Wood, T D

The focus of this dissertation is the utility of laser desorption Fourier transform ion cyclotron resonance (LD/FT/ICR) mass spectrometry as a tool in analyzing high mass ions. Improved sensitivity for laser desorption is demonstrated when a solid state NH[sub 4]Br is coadded to aromatic hydrocarbon samples. The laser desorbs the salt into its ionic components; the cationic NH[sub 4][sup +] acts to selectively protonate neutral hydrocarbons generated by laser desorption via chemical ionization (LD/CI) to form (M + H)[sup +]. Laser desorption is also a useful tool for fullerene soot analysis. Small fullerenes coalesce to form even-numbered giant carbon clusters not originally present in the soot (C[sub n], N [ge] 100) in the positive ion mode when fullerene soots are applied as thick films. Toluene extracts of the soots heated in pressure bombs examined in positive and negative ion modes exhibit similar qualitative distributions of fullerene ions, provided thin-film conditions are maintained. Heretofore undiscovered dehydrogenated toluene-fullerene adducts (C[sub 2n]C[sub 7]H[sub 6], 102 [ge] 2n [ge] 60) were discovered in the bomb extracts. Derivations of the upper mass limits for matrix-assisted laser desorption FT/ICR showed that the axial upper limit is responsible for the poor mass range performance of this technique. Based on radial and axial limits, optimal trapping voltages were derived. The upper limit is increased by using high trapping voltages, gated trapping, and collisional cooling. Collisional cooling combined with quadrupolar excitation was shown to be an effective means of axializing ions for efficient sustained ion trapping with high mass resolving power and single-isotope ion isolation selectivity. The selectivity advantages was explored in detail.

• Research Organization: Ohio State Univ., Columbus, OH (United States)
• OSTI ID: 7015762
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AMMONIUM COMPLEXES
BROMIDES
BROMINE COMPOUNDS
CARBON
COMPLEXES
ELEMENTS
FOURIER TRANSFORM SPECTROMETERS
FULLERENES
HALIDES
HALOGEN COMPOUNDS
ION CYCLOTRON RESONANCE SPECTROSCOPY
ION SPECTROSCOPY
LASER SPECTROSCOPY
MASS SPECTRA
MEASURING INSTRUMENTS
NONMETALS
SPECTRA
SPECTROMETERS
SPECTROSCOPY
TRAPPING