22 food hygiene & safety
100
major reason, why the number of identified components
80
60
R = 15,000 in the case of R = 15 000 decreases disproportionately to
329.00647
40 Not detected
Relative
100
Abundance
20 the measurements at higher resolving power (Fig. 5).
0
80
100
4.89
For this reason, a dilution series was measured
80
60
60
R = 50,000 at higher resolution settings. One example
40
40
Relative
Abundance
20
(Metabenthiazuron) is shown in Fig. 7. It demonstrates
0
20
3 4 5 6 7
excellent linearity and sensitivity down to 2 ppb level
Relative Abundance
Time (min)
0
(2ng/mL).
329.00510
100
80
Conclusions
60 329.02475 p New Exactive mass spectrometer demonstrates
40
C
14
H
14
O
5
CIS
0.76 ppm
superior mass resolving power compared to that
20 328.98993
329.09021 obtained using TOF instruments.
0
p High resolving power (up to 100 000) provides
328.95 329.00 329.05 329.10
m/z precise mass accuracy for complex sample analysis
p High resolving power provides excellent sensitivity,
Fig. 6. Expanded view of the pesticide mixture at different resolution linearity and selectivity in multi-residue screening of
settings (top: 15 000 and bottom: 50 000). Pesticide Sulcotrion complex matrices.
(m/z 328.02475) is masked under background ions at a resolution p Fast scan speed (10 Hz) are fully compatible with the
of 15 000 but is easily detected at 50 000 resolution (see also mass use of U-HPLC fast chromatography methods
chromatogram inset). For the analysis of very complex samples it is
advantageous to select the appropriate scan speed
☞
window of 3ppm at higher resolution setting.
and resolution in order to avoid unresolved isobaric
This is exemplified in Fig. 6, where extracted ion
compounds (matrix ions from analyte ions) and
chromatograms of Sulcotrion at 50 ppb for R = 15 000
still allow unambiguous detection of low abundant
and R = 50 000 are shown. The higher resolved
species. p
spectrum displays two peaks, of which the smaller one is
Sulcotrion.
Markus Kellmann, Andreas Wieghaus, Helmut Muenster,
The lower resolved peak masks the pesticide signal
Thermo Fisher Scientific, Bremen, Germany; Lester Taylor,
completely. The only indication for the presence of
Dipankar Ghosh, Thermo Fisher Scientific, San Jose, CA, USA.
Sulcotrion is a slightly broader peak or shoulder and a
www.thermofisher.com. Acknowledgements: The authors would
mass shift of the interfering ion towards higher masses.
like to thank Paul Zomer and Hans Mol from the RIKILT
This would lead to a false negative result, if the analysis
Institute for Food Safety in Wageningen, The Netherlands, for
was only performed at a resolution of 15 000 and is the
providing the samples.
Fig. 7. Quantitation curve for Metabenthiazuron ranging from 2 to 250 ppb. The quantified peak for each concentration level
demonstrates the high quality data even at the lowest level.
www.scientistlive.com
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