3
Figure 1. AutoSRM Precursor Ion Selection for NDMA from EI full scan spectra
Figure 2. AutoSRM collision energy optimization for all nitrosmaine precursor ions
3. Optimize for all compounds the collision energy of
the selected precursor/product ion transitions for
maximized compound response and best method
sensitivity (Figure 2).
Initiated by the AutoSRM procedure as many as
necessary autosampler injections from the one standard
vial are scheduled.
As a result of the AutoSRM program, the generated SRM
transition table shown in Table 1 has been automatically
built. The table represents at the same time the TSQ 8000
GC-MS/MS system MRM acquisition method using
the timed-SRM mode with a short acquisition window
of 60 s around the compound retention time. No other
setting of scan segments is necessary, or will be necessary
in case additional compounds need to be added to the
acquisition, other than the compound retention time.
Sample Measurements
From the large variety of potential nitrosamines the
compounds that had been included in this method
are those that are reported to be of relevance in the
germinated malt drying process. Samples analyzed
included malt beer as unspiked samples and 4% ethanol
as sample blanks. In case of the analysis of other food
matrices, additional compounds can be added to this
method easily at any time as described in the method
setup by AutoSRM
[9, 10]
.
Results
The chromatograms of the nitrosamines included in this
method show a quick elution of the compounds from 7.87
min NDMA to 12:47 min allowing a short cycle time for
increased sample throughput. The peak intensities are
retained in Figure 3 at the lowest calibration level of 1
ppb. NDMA can be detected with good S/N values.
8
9
10
11
12
Time (min)
0
20
40
60
80
100
Relative Abundance
RT: 7.87
AA: 6336
SN: 31
RT: 8.55
AA: 32766
SN: 231
RT: 9.75
AA: 1657812
SN: 2695
RT: 11.35
AA: 23756
SN: 26
RT: 11.80
AA: 25711
SN: 10
RT: 12.06
AA: 22994
SN: 4
RT: 12.47
AA: 100389
SN: 40
NDMA
NDEA
NDPA (ISTD)
NDBA
NPIP
NPYR
NMOR
Figure 3. Chromatogram of the standard mix at 1 ppb
NPIP
NDBA
NMOR
NPYR
