Presentation given at HTC-13 in Bruges, Belgium, on Markes' BenchTOF time-of-flight mass spectrometers for gas chromatography. As well as the features that make BenchTOF essential in the modern laboratory, the presentation describes Select-eV – newly launched variable-energy electron ionisation technology for GC–MS. Many examples are provided that illustrate how both classical reference-quality EI mass spectra at 70 eV and enhanced molecular ions at lower energies can enhance detection of challenging analytes – all without any loss in sensitivity.

1. Select-eV – Shaping the future of GC–MS
Laura McGregor, Nick Bukowski

2. What is the BenchTOF?
•
A reflectron time-of-flight mass spectrometer
•
Platform-neutral
•
Innovative design

3. BenchTOF technology
Innovative design
Differentially pumped source
and analyser chambers
High
accelerating
voltage
Direct extraction optimises
sensitivity
Multi-stage reflectron
optimises resolution

4. The result…
…exceptional sensitivity for trace analytes
RT: 3.50 - 5.65
NL:
3.62E4
m/z=
271.50272.50 MS
100812_13_
dbc_100812
154612
5.23
100
90
80
Relative Abundance
70
OFN 1 pg
60
50
40
30
20
10
0
3.60 3.72
3.6
Base Peak
Retention Time : 5.23
Scan : 628
Intensity : 36173
3.86 3.95
3.8
4.0
4.22 4.33
4.2
4.47 4.50 4.68
4.4
4.6
Time (min)
4.8
4.95
5.0
5.19
5.2
Calculated values
Noise Range : 3.99 - 4.19 minutes (24 scans)
Baseline : 6
Signal To Noise : 2747
Standard Deviation : 13
5.48
5.4
5.6

5. Exceptional sensitivity
Trace-level pesticides (20 pg of aldrin; EIC m/z 263)
SIM quadrupole
S/N ratio: 41
2 pg on column
S/N ratio: 30
BenchTOF
S/N ratio: 380

6. Variable-energy electron
ionisation with no loss in
sensitivity

7. Advantages of Select-eV ionisation
•
No source exchanges or reagent gases
•
No loss in sensitivity
•
Enhanced molecular ions and reduced fragmentation
•
No ionisation of carrier gas/background gases
•
Reduction of matrix impact
Enhanced signal-to-noise and lower LoD for target analytes

8. Variable-energy ionisation
Transition of fragmentation pattern aids structural elucidation
70 eV
16 eV
12 eV

9. Select-eV ionisation of alkanes
Pentacosane (C25H52)
70 eV
Molecular ion: 1.5%
(800 counts)
14 eV
Molecular ion: 26%
(4000 counts)

10. The full presentation can be
downloaded from the Markes
website
http://www.markes.com/Resources/Scientificpublications/Conference-presentations.aspx

11. Contact Markes
enquiries@markes.com
www.markes.com