Thermo Scientific Prima PRO, Руководство пользователя

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Startup & Shutdown
Procedure
Thermo Fisher Scientific Prima PRO & Sentinel PRO Mass Spectrometers User Guide 7-9
The Mass Alignment tab ( Figure 7–10 ) is used to display peaks over
a defined mass range in a similar way to that used on the Peak Shape
tab . In this instance, a cursor is used to assign mass numbers to
identified peaks. Typically, two or three masses need to be ‘locked’
over the mass range of interest.
Figure 7
–10.
Mass Alignment tab
The Prima PRO mass position is related to magnetic field by the
following equation
mass = km x cm
where km is a constant of proportionality and cm is an offset, with
both of these constants having a slight mass dependency. Values of
km and cm are determined for adjacent pairs of locked masses; at
masses beyond the locked mass range, the values of km and cm are
taken from the closest locked mass pair. If an incorrect mass
assignment is made the mass table can be deleted and the process
repeated.
Since the Prima PRO instrument is a magnetic sector mass
spectrometer, which produces a focused ion beam at the detector, the
peak shape obtained is ‘flat-topped’, i.e. uniform response is
observed over a finite mass width, e.g. 0.3 amu at mass 28. Provided
the measurement taken at the mass of interest is on the peak’s flat
top, high precision analysis will be observed. If masses are aligned
within the central 2/3 of the flat top region, this is normally sufficient
to guard against any drift in the mass scale.