5
Acquiring ESI Sample Data Using the Tune Plus Window
Setting Up to Acquire MS/MS Data in the Full Scan Type
Thermo Electron Corporation
LTQ XL Getting Started
87
(
Normalization Level
and
Ion Time
), while you optimize the value of the
Isolation Width in the Define Scan dialog box, as follows:
a. In the Define Scan dialog box, in the MS
n
Settings group box, in the
Isolation Width box, type
3
to specify an isolation width of
m/z
3.
Then, click
Apply
.
b. In the Tune Plus window, observe the mass spectrum for the parent
ion of reserpine,
m/z
609.2. Ensure that the readback values for
NL
and
IT
are relatively stable.
c. Again, in the Define Scan dialog box, in the MS
n
Settings group
box, in the Isolation Width box, type
2.8
to specify an isolation
width of
m/z
2.8. Then, click
Apply
.
d. Repeat steps b and c above, entering successively smaller values for
Isolation Width. Continue to observe the intensity of the mass
spectrum of the parent ion, and ensure that the values for
NL
and
IT
are stable with each change you make to the Isolation Width.
8. In the Define Scan dialog box, in the MS
n
Settings group box, in the
Normalized Collision Energy box, type
20
to specify an initial value of
20 for the collision energy. Click
Apply
.
9. In the Tune Plus window, observe the mass spectrum of the product ions
of reserpine (or your analyte of interest). If necessary, increase the value
for the Normalized Collision Energy in increments of 5% to cause the
clear display of product ion mass spectrum. (After each change in value,
click
Apply
to implement the change.) See
Note
The optimum value for the Isolation Width is the smallest
m/z
width (instrument minimum width =
m/z
0.4) that gives a
mass spectrum of maximum intensity for only the ions of
interest. When the optimum Isolation Width is obtained the
values for NL and IT are stable and the mass peak for the parent
ion is at its maximum intensity and appears symmetrical. An
Isolation Width value that is less than the optimum value causes
a substaitial drop in the NL
reading. A significant drop in
sensitivity indicates that the ions of interest are not effectively
isolated.
Note
After the Isolation Width is optimized, you can
compensate for minor changes in tune stability by increasing the
Isolation Width value a small amount. This adjustment should
be no larger than
m/z
=1.
