Power
The power function calibration equation is:
y = ax
p
The equations for the linear calibration are used as described above to calculate the slope (m) and intercept (b),
except that x in those equations is replaced by ln x and y is replaced by ln y. When this is done, a and p are
calculated as:
a = e
b
p = m
If any of the x or y values are negative or zero, then an error is reported.
Wagner
The Wagner calibration equation is:
ln y = a
2
(ln x)
2
+ a
1
(ln x) + a
0
The equations for the quadratic calibration are used as described above to calculate a
0
, a
1
, and a
2
, except that x
in those equations is replaced by ln x and y is replaced by ln y.
If any of the x or y values are negative or zero, then an error is reported.
Hill
The Hill calibration equation is:
y = (a + bx
n
) / (c + x
n
)
It is not possible to provide an analytical function for solving for a, b, c, and n. Instead, the co-efficients are
determined using the iterative Levenberg-Marquardt method.
Qualitative Analysis
Qualitative analysis is the identification of a target or unknown compound. In mass spectrometry, determining
which compound is present is accomplished using mass accuracy, retention time, isotope pattern, library searching,
and formula finding. Using all of these tools together can increase the confidence in identifying both targeted and
non-targeted compounds in unknown samples.
Mass Accuracy
When trying to identify a known target compound in a sample, it is useful to look at the mass accuracy of that
compound and determine if a potential 'hit' for that compound has a mass accuracy within a certain tolerance.
For example, imazalil has a chemical formula of C
14
H
14
Cl
2
N
2
O, which gives it a mass of 296.0483, to four decimal
places. A protonated adduct is an ion with a positive charge that is normally detected using an accurate mass
time-of-flight instrument. The protonated adduct of imazalil has a mass 297.0556. If it is suspected that imazalil
is in a sample, then compare the mass of the compound found to the mass of the protonated imazalil and determine
SCIEX X500 QTOF System
System User Guide
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RUO-IDV-05-2334-E
Principles of Operation
