1
Introduction
Scan Modes
10
TSQ Quantum XLS and TSQ Quantum GC User Guide
Thermo Scientific
To detect an ion, between the time the ion leaves Q1 and enters Q3, it must lose a neutral
moiety whose mass (the neutral loss mass) is equal to the difference in the mass ranges being
scanned by the two mass analyzers. Thus, a neutral loss mass spectrum is a spectrum that
shows all the parent ions that lose a neutral species of a selected mass.
Note that a neutral gain (or association) experiment can also be performed in which the mass
range scanned by Q3 is offset by a selected mass above the mass range scanned by Q1.
For a neutral loss (or neutral gain) mass spectrum, as for a parent mass spectrum, data for the
mass-to-charge ratio axis are obtained from Q1 (the parent ion), whereas data for the ion
intensity axis are obtained from Q3 (the product ion being monitored).
Experiments that use the Neutral Loss scan mode (neutral loss experiments) are useful when a
large number of compounds are being surveyed for common functionality. Neutral moieties
are frequently lost from substituent functional groups (for example, CO
2
from carboxylic
acids, CO from aldehydes, HX from halides, and H
2
O from alcohols).
Figure 4.
Illustration of the Neutral Loss scan mode
Q1 Scanning
Q1 m/z
Q2
R F O nly + A r
Q3 = Q1 -
Δ