5-20 Calibration
scanning to slightly higher and lower masses than the mass window of
interest.
Before manually calibrating the instrument you first need to remove the Lock
Mass value in the TDC Settings dialog box and remove any existing
calibration file.
Using Dynamic Range Enhancement with calibrations
Dynamic Range Enhancement must not be used when acquiring instrument
calibration data. Signal intensities are kept low while calibrating the
instrument. Extended and normal dynamic range acquisitions can use the
same calibration file.
To turn Dynamic Range Enhancement off when acquiring data for
calibration:
1. In the GCT Premier Tune Acquire dialog box, ensure that Use DRE is
clear.
2. Click Calibration.
To manually calibrate the instrument:
1. In the TDC Settings dialog box, Centroiding Parameters pane, set
Lock Mass to 0.
See also: Configuring the TDC settings on page B-11.
2. In the Tune window Calibration tab, click Remove Calibration.
3. Using a septum piercing syringe, inject approximately 0.2 µL of
heptacosa into the reference reservoir inlet cap.
See also: Introducing the reference sample on page 3-6.
4. Ensure that the beam is not saturated.
Tip: Ensure the largest peak is approximately 1000 counts per second on
the Tune window in continuum mode. The peak is saturated if a
question mark (?) is displayed above it, when displayed as a single the
spectrum in centroid mode.
See also: Effects of saturation on peak shape on page B-51.
5. Ensure you count all the ions by setting-up the MCP and TDC Threshold
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