
Chapter 7 PSD Analysis
7-8 PerSeptive Biosystems
7
7.1.4 Mass Calculation for Fragment Ions
PSD calibration
equation
PSD calibration specifies the mass of a fragment ion as a
function of:
• Mass and flight time of the precursor ion
• Mirror Ratio setting
•
α
,
β
, and
γ
calibration constants
The equation that the Voyager software uses to calculate the
mass for fragment ions is shown below:
Default PSD
calibration
If you select default PSD calibration, the Voyager software
uses the calibration equation above and substitutes the
following values for calibration constants:
•
α
—Calculates from instrument geometry
•
β
and
γ
—Uses zero (0)
where:
t
p
m
p
α
,
β, γ
t
f
Fragment ion flight time
m
f
Fragment ion mass
Calibration constants=
=
=
=
R
i
= Mirror Ratio
=
m
f
=
(
α
R
i
+
β
)
[(
t
f
– t
p
) +
γ
(
t
f
– t
p
)
2
] +
α
R
i
+
β
α
+
β
m
p
Precursor mass entered in Instrument Settings (see page 7-26)
Precursor ion flight time (at R
i
=1), calculated using the standard
calibration equation (described on page 6-9)
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