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Performance of a Hybrid RF/DC Quadrupole-Linear Ion Trap Mass Spectrometer

Performance of a Hybrid RF/DC Quadrupole-Linear Ion Trap Mass Spectrometer James W. Hager MDS SCIEX ASMS, 2002 Outline Linear ion trap mass spectrometer concept. Mass selective axial ion ejection. Marriage with triple quad ms. Trapping and extraction efficiencies Space charge effects

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Performance of a Hybrid RF/DC Quadrupole-Linear Ion Trap Mass Spectrometer

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  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. Q0 Q1 Q2 Q3 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. “Ion bottles” for optical spectroscopy. Minimize fringing fields to maximize performance. Ion accumulation for enhanced ms sensitivity. Mass analyzers: RCM, 2002, 16, 512-526. JASMS, 2002, 13, 659-669. Linear Ion Traps

  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. Linear Ion Trap Mass Spectrometer Drive RF & auxiliary AC

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

  8. Time Averaged Axial Electric Field Dehmelt approx.: radial amplitude fringing field F. Londry, ASMS, 2002 .

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

  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. eV frags. Hybrid Approach to Product Ion MS/MS • RF/DC Q1 Q2 Q3 linear trap 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 N2 CAD Gas Exit lens Aux AC Ion accumulation Q0 Q3 Q1 Q2 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 QqQ Reserpine – Product Ion Q1 Open Resolution Enhanced Product Ion Scan > 350x

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

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

  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

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