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Transpector MPS Operating Manual
characteristic provides a good degree of peak separation throughout the mass
spectrum, but results in an ion transmission efficiency (i.e., the fraction of all ions
of the selected mass entering the mass filter which are transmitted through it) that
decreases as mass increases.
The way the mass scale is
calibrated
or
tuned
(i.e., the way the peak positions and
widths are adjusted) can have a significant effect on the transmission efficiency of
the mass filter across the mass spectrum. If the adjustments are not made properly,
the ratios of peak heights across the mass range will not be correct.
4.1.3.3 Fragmentation Factors
The fragmentation factor is the fraction of the total ion current contributed by ions
of the chosen mass. Only peaks contributing at least one percent to the total ion
current are included in the list. The sum of the factors for all the peaks in a mass
spectrum cannot exceed 1.00. The sum can be less than 1.00 if only some of the
peaks are listed (either there are many peaks, or some of the ions produced lie
outside the mass range of the particular instrument used).
The data presented earlier in
for the major peaks of some common substances
, is compiled from more than one
source and is for illustrative purposes only. For maximum accuracy in determining
partial pressures, the fragmentation factors for the substances of interest should be
measured with the same instrument, and the same adjustments, as the samples to
be analyzed.
