1. Performance of a Hybrid RF/DC Quadrupole-Linear Ion Trap Mass Spectrometer
James W. Hager
MDS SCIEX
ASMS, 2002

2. Outline Linear ion trap mass spectrometer concept.
Mass selective axial ion ejection.
Marriage with triple quad ms.
Trapping and extraction efficiencies
Space charge effects
Performance characteristics.
Future directions.

3. Triple Quad. MS/MS --Tandem in Space
Only 1 ion pair is stable at any one time.
Poor scanning efficiency.
Very efficient for MRM.
Very selective scans available.

4. 3D Ion Trap MS/MS --Tandem in Time
Full mass spectrum for each pulse of ions.
High scanning efficiency.
Scanning instrument only.

5. Linear Ion Traps “Ion bottles” for optical spectroscopy.
Minimize fringing fields to maximize performance.
Ion accumulation for enhanced ms sensitivity.
Mass analyzers:
RCM, 2002, 16,
JASMS, 2002, 13,

6. Linear Ion Trap Mass Spectrometer
Ions are trapped by barriers:
Radially: RF potential
Axially: DC barriers
Radial RF determines the ion frequencies of motion.
Radial and axial ejection demonstrated.
Drive RF &
auxiliary AC

7. RF Fringing Fields Axial Ion Ejection:
Exit fringing fields couple radial/axial degrees of freedom of the trapped ions.
Excite ions radially to eject them axially.

8. Time Averaged Axial Electric Field
Dehmelt approx.:
radial amplitude
fringing field
F. Londry, ASMS,

9. Hybrid Instrument with Q3 Linear Ion Trap MS
N2 CAD Gas
linear ion trap
3x10-5 Torr
Aux AC
IQ2
IQ3
Exit
Skimmer
Orifice
LINAC
IQ1 Q0 Q1 Q2 Q3

10. Q3 Trapping Efficiency vs. Chamber Pressure

11. Extraction Efficiency vs. Ejection q-Value
(4x10-5 Torr)

12. Trapping & Extraction Efficiencies
5-inch long rod array:
Trapping efficiency: ~45%
4x10-5 Torr background pressure
Extraction efficiency: 16-20%
q-value dependent
Overall efficiency: ~8%

13. Hybrid Approach to Product Ion MS/MS
RF/DC Q Q Q3 linear trap eV
frags.
Advantages:
No time required to isolate the precursor ion.
No loss for isolation of fragile precursor ions.
The ion trap is filled with only precursor and fragment ions.
Triple quad. fragmentation patterns.
No inherent low mass cut-off.

14. Product Ion Scanning Precursor ions selection in Q1.
N2 CAD Gas
Aux AC
Exit lens
Ion accumulation Q0 Q1 Q2 Q3
Precursor ion
selection
Fragmentation
linear ion trap
3x10-5 Torr
Precursor ions selection in Q1.
Fragmentation in Q2.
Trap products in Q3.
Mass scan.
Concurrent trapping in Q0.

15. Sensitivity Enhancements
Reserpine – Product Ion
QqQ
Q1 Open Resolution
Enhanced Product Ion Scan
> 350x

16. Sensitivity Enhancements—Reserpine
Q1 Open Resolution
QqQ
Enhanced Product Ion Scan

17. Enhanced Prod Ion Scan – 75eV
No Low Mass Cut-off
Taurocholic Acid–
Product Ion
LCQ Deca – 45% CE
3 amu isolation width
Enhanced Prod Ion Scan – 75eV

18. Resolution and Scan Speed: Reserpine
4000 amu/sec
~0.55 amu wide
1000 amu/sec
~0.35 amu wide
250 amu/sec
~0.15 amu wide

19. Mass Shift vs. Ejection q-Value
3.5x10-5 Torr
103X Change of Ion Current

20. Mass Shift vs. Input Ion Intensity
q=0.86, m/z=609

21. Space Charge Effects Q3 Space Charge Effects (3x10-5 Torr): D~0.02 amu
104x > ion current
D~0.02 amu

22. RF/DC Quadrupole-Linear Ion Trap Mass Spectrometer
Ion trap and triple quad capabilities on a single platform.
High sensitivity ion trap scans:
Single MS survey scans
Product ion scans
MS3 in Q3
Triple quad. Functionality:
MRM
Precursor ion scans
Neutral loss scans

23. Future Directions
Tandem-in-space ion trap(s) approach allows for simultaneous ion processing while the primary mass analyzer is scanning.
Increased sample utililization eff. and thus higher duty cycles.
Very high resolution.

24. Acknowledgments Yves LeBlanc Frank Londry Bill Stott Bruce Collings
John Vandermey