Analytical Seminar - Literature
John Carr
October 24, 2003
Ion Trap Mass Spectrometry of Fluorescently Labeled Nanoparticles1
Accurate molecular weight determinations of macromolecular ions with mass
ranges in the mega-Dalton (MDa) range are limited in conventional mass spectrometry by
a loss in detector efficiency due to the lower impact velocities of large ions.2
Electrospray ionization methods generates ions with a mass to charge (m/z) ratio that
allow detection by conventional methods yet generate complicated spectra with
decreasing resolution on the high mass end.1,3,4 In this paper, matrix-assisted laser
desorption/ionization (MALDI) generates 27 nm ions of fluorescently labeled
polystyrene spheres with an average mass of 6.5 MDa.1,5 A dual quadrupole ion trap is
utilized where the first trap provides mass discrimination while the second concentrates
the ions ejected from the first to be detected through laser induced fluorescence (LIF).
Several experimental parameters related to both ion traps are optimized and theoretically
discussed. Results of the polystyrene particle mass analysis yield theoretically accurate
data with high signal to noise ratios. Application of this technique to a biological
molecule was illustrated with the mass determination of fluorescently labeled IgG (goat
anti-mouse antibody). Results showed a signal to noise ratio of 10 with a mass resolution
greater than five at 1.5 * 105 Da. A brief overview of the problems related to high
molecular weight determinations using conventional techniques2,6 will be presented in
addition to a description of the dual ion trap experimental setup and parameters. The
experimental results and implications will be discussed and direction of further work
outlined.
References:
1. Y. Cai, W.P. Peng, and H.C. Chang, Anal. Chem. 75, 1805 (2003).
2. I.S. Gilmore and M.P. Seah, Int. J. Mass Spectrom. 202, 217 (2000).
3. T. Nohmi and J.B. Fenn, J. Am. Chem. Soc. 114, 3241 (1992).
4. X. Cheng, R. Bakhtiar, S. Van Orden and R.D. Smith, Anal. Chem. 66, 2084
(1994).
5. Y. Cai, W.P. Peng, S.J. Kuo, C.C. Han, and H.C. Chang, Anal. Chem. 74, 4434
(2002)
6. D.C. Shriemer and L. Li, Anal. Chem. 68, 2721 (1996).