Set up a 1 box display on the tune page and set
Function
to
MS Scan
.
Observe the candidate parent ion in the display and determine its nominal mass.
In this example the reserpine ion at
z
609 is used as a model parent.
The accurate top of the parent ion can be found experimentally by performing a
“daughter ion scan” over a restricted mass range in the absence of collision gas.
On the tune page set
Function
for peak 2 to
Daughter Scan
.
Place the mouse cursor on the
Set
mass for peak 2 and type in the nominal mass
of the parent ion selected by MS1, in this case 609.
Vary the
Set
value between 608.5 and 609.5 while optimising the intensity of
the non-fragmented parent ion in the tune display.
The
Set
mass giving maximum intensity is used for future MS-MS experiments.
Fragmentation
Set up a wide range daughter ion scan by adjusting the
Mass
and
Span
parameters for peak 2.
At this point, with the collision gas off, a few daughter ions of low intensity may be
visible. These are the products of unimolecular dissociations.
Argon (99.9% pure) is recommended as the collision gas.
Select
Gas
,
Collision Gas
.
Adjust
CID Gas
on the front panel to admit sufficient gas to attenuate the
parent ion peak by about 50%.
Adjust the
Entrance
,
Collision
and
Exit
parameters in the
Analyser
menu to
produce the desired degree of fragmentation. (These parameters are interactive in
MS-MS operation.)
In daughter ion analysis maximum transmission (sensitivity) can be achieved by the
following adjustments:
•
Optimising
Collision
.
•
Optimising
Exit
.
•
Optimising
Entrance
.
•
Optimising the collision gas pressure using the
CID Gas
needle valve.
Additionally, transmission can be improved at the expense of specificity by reducing
HM Resolution 1
and increasing
Ion Energy 1
on the
Analyser
window. In most
cases, where chemical interference with the parent ion is not acute, the loss of
specificity is negligible.
Routine Procedures
Page 45
Quattro Ultima
User's Guide
Содержание Quattro Ultima
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