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Enhancing General Unknown Screening with Data Independent Analysis on a Quadrupole Orbitrap Mass Spectrometry System
Overview
Purpose: Enhance the unknown screening
capabilities over the classical All Ion Fragmentation
approach
.
Methods:
Envoironmental samples were measured with
different scan methods for comparison.
Results:
The DIA mode serves for the most versatile data
suitable for unknown screening as well as for targeted
quantitation at the same time
Introduction
In residue analysis of environmental and food samples
the need exists for the analysis of larger sets of analytes
at the same time. Recent developments in scan speed of
triple quadrupole mass spectrometry systems have
fuelled this development, but even more the steadily
increasing use of high resolution accurate mass (HRAM)
mass spectrometry instrumentation (mainly TOF and
Orbitrap
TM
based instruments) in residue analysis leads to
numerous new options in this field as well into new
challenges. One of these challenges is the confirmation
step for the analytes, since precursor ion selected
fragmentation comes to its technical limits in terms of the
number of analytes and becomes impossible in case of
analytes yet unknown or disregarded. The alternative of
fragmentation without precursor ion selection (as “All Ion
Fragmentation” or “MS
E
”) has proven to be very powerful
but still faces some limitations in sensitivity of fragments
for low concentrated components. In the Data
Independent Acquisition (DIA) scan mode of a Thermo
Scientific
TM
Q Exactive
TM
mass spectrometric system, the
full scan mass range is divided into smaller ranges,
typically in the range of 50 to 100 Daltons. This enhances
the dynamic range for the fragment scans, resulting in
significant higher sensitivity of the significant fragments
needed for compound confirmation. At the same time all
options for suspect screening or even General Unknown
Screening remain fully available as in AIF.
Methods
Sample Preparation
Ground water, surface water and waste water samples
were collected and prepared as described earlier
1
.
Liquid Chromatography
For chromatographic separation, a HPLC system was
used consisting of a CTC Pal autosampler (CTC analytics,
Results
All Ion Fragmentati
First, data was acqui
acquisition, extracted
for the quasimolecul
of compounds. Fig. 3
Sotalol as an exampl
completely and som
the one of the quasi
intensity is significant
the used standard w
DIA Mode
In DIA mode different
assumption was that
resulting isolation wi
on the fragment ion s
the smaller masses
shows only low amou
FIGURE 2. Gradient
separation.
RT:
0.03 - 2.47
0.5
1.0
1.5
2.0
Time (min)
0
20
40
60
80
100
0
20
40
60
80
100
0
20
40
60
80
100
0
20
40
60
80
100
RelativeAbundance
0
20
40
60
80
100
0
20
40
60
80
100
1.34
1.32
1.34
1.30 1.36
1.29 1.37
1.28
1.40
1.27
1.43
1.26
1.48
1.56
1.24
1.66 1.84 2.3
1.34
1.33
1.35
1.29 1.38
1.28
1.42
1.27
1.50
1.54
1.35
1.29
1.40
1.51
1.33
1.31
1.34
1.30
1.37
1.41
1.28
2
1.44
1.32
1.36
1.30
1.37
1.27
1.40
1.26
1.43
1.26
1.54 1.61
FIGURE 3. Parent io
Morphine (A) and S
A