Agilent 6500 Series Q-TOF LC/MS Maintenance Guide 41
Maintenance 2
To prepare the reference mass solution
Before you break open each ampoule, invert the ampoule several times to
mix. Inspect the ampoule's contents to ensure that all the solution is
contained in the lower cylindrical base. Shake the ampoule, if needed, to
dislodge any air pocket that may prevent solution from settling in the lower
portion of the ampoule.
4 Cap and invert the bottle several times to thoroughly mix the reference
mass solution.
5 Transfer 100 mL of this solution to CDS Reference Bottle “A”.
Use of ES-TOF Reference Mass Solution
Use these guidelines to adjust the amounts of IRM compounds to add to this
preparation.
• IRM abundances less than 1000 counts generally do not yield acceptable
ion statistics for good correction. Ideally, abundances will be at the level
of 10,000 counts or greater at any point in the analysis where correction
is desired.
• The abundances of the reference mass compounds change during an
HPLC gradient, with lesser abundances occurring at higher organic
compositions. This is especially true when using acetonitrile as the
organic component. Make sure the abundances are high enough during
the entire gradient.
• Interference at one of the reference masses can cause problem with mass
accuracy, most likely the reference mass 121 m/z at the low end of the
scan range, where the background response is the highest. This causes
an error in determining that reference mass value, leading to an error in
assignment of other mass peaks in that scan. Sometimes, the problem
can be lessened by increasing the amount of that reference mass
component. Sometimes a different compound can be chosen to serve as
the reference mass compound (e.g., a phthalate response at 391.284286
m/z). More often, the problem is remedied by altering the sample cleanup
procedures to remove the interfering component(s).
• The values chosen for the reference mass correction depend on the
adducts present during the analysis. Refer to the instruction sheet
included with the internal reference mass kit for the accurate m/z values
of the most common adducts.
• For instruments with Agilent Jet Stream Technology only: Higher sheath
gas temperatures and sheath gas flows will increase the response of the
922 m/z reference mass compound.
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