Voyager DP-263-S Guía de usuario Pagina 41

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Voyager-DE™ (Delayed Extraction™) Technology
Voyager
Biospectrometry
Workstation User’s Guide 1-11
1
1.4 Voyager-DE
(Delayed Extraction
) Technology
In this section
This section describes:
Limitations of MALDI technology
Delayed Extraction
Delayed Extraction versus Continuous Extraction
Benefits of Delayed Extraction
Velocity focusing
Limitations of
MALDI
technology
In traditional MALDI, ions exhibit a broad kinetic energy
distribution which is largely due to the initial velocity imparted
to ions during the desorption/ionization process. This initial
velocity of desorbed analyte ions is nearly independent of
mass of the analyte and the initial kinetic energy is
proportional to the mass. In addition, when desorption occurs
in a strong electrical field, energy is lost by collisions with the
neutral plume, and further mass-dependent energy dispersion
results.
According to the theory of “time-lag energy focusing” as
originally developed by Wiley and McLaren
1
, the dependence
of ion flight time on initial velocity can be corrected, to the first
order, by delaying the extraction of ions from the source. If
higher order terms are insignificant, then the mass resolution
should be determined by the ratio of the total flight time to the
uncertainty in the time measurement. The observed mass
resolution should increase in proportion to the effective length
of the ion flight path.
1. W. C. Wiley and I. H. McLaren,
Rev. Sci. Instrum
., 1953, 26, 1150-1157,
W. C. Wiley, U.S. Patent 2,685,035.
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