Thermo Scientific TSQ Altis, Руководство по оборудованию

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17
Scan Types
Neutral Loss Scan Type
76 TSQ Altis, Quantis, and Fortis Hardware Manual Thermo Scientific
As a result, the neutral loss scan type provides two stages of mass analysis. In the first stage, the
precursor mass analyzer (Q1) separates ions that form in the ion source by their
m/z values.
These ions enter the collision cell.
In the second stage of analysis, ions in the collision cell can fragment further by metastable ion
decomposition or by CID to produce product ions. The product mass analyzer then separates
these product ions by their
m/z value.
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. Therefore, a neutral loss mass spectrum is a spectrum that
shows all the precursor ions that lose a neutral species of a selected mass.
You can also perform a neutral gain (or association) experiment 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 precursor mass spectrum, Q1 (the
precursor ion) provides data for the
m/z axis, whereas Q3 (the product ion being monitored)
provides data for the ion intensity axis.
You can use experiments that use the neutral loss scan type (neutral loss experiments) when
surveying a large number of compounds for common functionality. However, you frequently
lose neutral moieties from substituent functional groups (for example, CO
2
from carboxylic
acids, CO from aldehydes, HX from halides, and H
2
O from alcohols). Figure 40 shows a
common fragment ion.
Figure 39. Illustration of the neutral loss scan type
Q2
RF Only + Ar
Q1 Scanning Q3 = Q1 -
Δ
Q1
m/z