5-2 Calibrating the instrument
Calibration files
Two types of calibration file exist:
• .sircal files are used for SIR experiments. They comprise the actual and
apparent reference masses for all the functions in the SIR experiment.
See “Calibrating the instrument for SIR experiments” on page 5-2.
• .scl files are used for scanning experiments. They comprise the
polynomial function that corrects the apparent masses in the acquired
data to give the actual masses.
See “Calibrating the instrument for scanning experiments” on page 5-5.
Calibrating the instrument for SIR experiments
Use selected ion recording (SIR) experiments monitor specific analytical
masses or reactions. You can monitor up to 32 SIR masses within a single
function. This method of acquisition is more sensitive than scanning, because
the instrument spends significantly more time at the mass of interest.
For SIR analyses you must calibrate the instrument prior to acquiring the
data.
The instrument supports two SIR methods supported, voltage SIR (VSIR) and
multiple reaction monitoring (MRM). VSIR is the more commonly used.
Calibration performs a voltage scan over each reference mass through the
experiment file’s mass range. All the reference masses within, and those just
outside, the range are detected.
Rule: Before starting the calibration, ensure that the instrument is still
correctly tuned by opening the instrument parameter file (.ipr) that has been
specified for the experiment (see Chapter 2).
To calibrate the instrument
1. In the MassLynx Tune window, click .
Alternative: Click Options > Experiment Calibration.
2. In the Experiment Calibration dialog box, click Browse to select the
experiment file created in “To save the experiment file” on page 3-38
step 2 (that is, VSIR Experiment.exp).
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