Agilent 6500 Series Q-TOF LC/MS Maintenance Guide 37
Maintenance 2
To prepare tuning mix
b Allow at least one minute for the tuning mix to flush the previous
solution from the calibrant system before you tune the instrument.
Store the custom tuning mix in the refrigerator when it is not being used for
extended periods of time.
Use these guidelines to adjust the custom tuning mix:
• In the final tune report, make sure all abundances listed in the report are
between 50,000 and 700,000 counts for proper calibration of the mass
axis. Dilution of the tuning mix up to 200-fold can be needed for
instruments with exceptional sensitivity. Be careful in your laboratory
work when you dilute greater than 50-fold because contamination and
sodium trifluoroacetate adducts can become problematic at higher
dilutions.
• The amount of water added affects the response of 118 m/z, with higher
amounts yielding a greater response and vice versa. You can add water
up to the amount of 5% (v/v). Do not add more water than that because
some components of the tuning mix can precipitate under these
conditions.
• If tune mass abundances are less than 10,000 counts, the tuning mix is
overdiluted. Dilutions at this level can result in poor mass accuracies.
• Use the HP-321 solution in a 2000:1 (v/v) ratio to the ESI-L Tuning Mix.
(If 10 mL ESI-L Low Concentration tuning mix is used, add 5 µL of the
HP-321 solution.)
• Sodium TFA can cause problems during calibration, depending on how
the calibrant is diluted and how much sodium is in the water. Table 5
lists the ions that can result from sodium TFA (both positive and
negative mode).
*
Table 5 Elemental compositions and calculated masses of sodium trifluoroacetate ion
clusters by electrospray ionizationunder positive-ion ([(CF3COONa)nNa]1) and
negative-ion ([(CF3COONa)nCF3COO]2) modes
n Positive-ion calculated mass Negative-ion calculated mass
1 158.96458* 248.96036*
2 294.93939* 384.93466*
3 430.91420* 520.90947*
4 566.88900* 656.88427*
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