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

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Presentation on theme: "Performance of a Hybrid RF/DC Quadrupole-Linear Ion Trap Mass Spectrometer James W. Hager MDS SCIEX ASMS, 2002."— Presentation transcript:

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. Q0Q1Q2Q3

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, –JASMS, 2002, 13, Linear Ion Traps

6 Linear Ion Trap Mass Spectrometer 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 fringing field radial amplitude F. Londry, ASMS, Dehmelt approx.:

9 Hybrid Instrument with Q3 Linear Ion Trap MS N 2 CAD Gas linear ion trap 3x10 -5 Torr Aux AC IQ2 IQ3 Exit Skimmer Orifice LINAC IQ1 Q0Q1Q2Q3

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 Q1 Q2 Q3 linear trap frags. eV 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 1.Precursor ions selection in Q1. 2.Fragmentation in Q2. 3.Trap products in Q3. 4.Mass scan. 5.Concurrent trapping in Q0. Q1 Q3 Q0 N 2 CAD Gas Q2 linear ion trap 3x10 -5 Torr Precursor ion selection Ion accumulation Fragmentation Exit lens Aux AC

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

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

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

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

19 Mass Shift vs. Ejection q-Value 3.5x10 -5 Torr 10 3 X Change of Ion Current

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

21 Space Charge Effects 10 4 x > ion current  0.02 amu 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 MS 3 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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