B-50 The MassLynx Tune window
However, MassLynx incorporates digital dead time correction (DDTC™),
which compensates for these effects and enables you to achieve accurate mass
measurement and quantitation over a large range of ion currents.
See also:
• Setting the Np multiplier on page B-50
• Effects of saturation on peak shape on page B-51
• Setting up resolution for dead time correction manually on page B-48
Setting the Np multiplier
To set the Np Multiplier:
1. In the TDC Settings dialog box, set the Np Multiplier to 1.0.
2. Introduce reference sample tris (trifluoromethyl) triazine.
See also: Introducing the reference sample on page 3-6.
3. Acquire data for calibration.
See also: Acquiring data for calibration on tab 5-16.
4. Display a single spectrum.
5. In the Spectrum window, click to view the spectrum in real-time.
6. When the peak at m/z 285 appears with the question mark over it,
reduce the intensity of the peak by opening the reference reservoir valve
until the moment when the symbol disappears.
Rationale: Saturation is indicated when a peak appears with a question
mark above it. When setting Np the signal must be strong, but not
saturated so that some dead time effect will be seen on the large isotope.
7. Recalibrate using the method above and the metri.ref reference file and
examine the residuals in the calibration output.
Consider the residuals field in the calibration display:
• If the first isotope marker lies below the line of best fit compared to
the second isotope marker, insufficient dead time correction is
applied. Decrease Np multiplier by 0.1, and repeat steps 3
through 7.
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