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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 l.jpg

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

James W. Hager

MDS SCIEX

ASMS, 2002


Outline l.jpg
Outline Mass Spectrometer

  • 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.


Triple quad ms ms tandem in space l.jpg

Q0 Mass Spectrometer

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.


3d ion trap ms ms tandem in time l.jpg
3D Ion Trap MS/MS --Tandem in Time Mass Spectrometer

  • Full mass spectrum for each pulse of ions.

  • High scanning efficiency.

  • Scanning instrument only.


Linear ion traps l.jpg

“Ion bottles” for optical spectroscopy. Mass Spectrometer

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


Linear ion trap mass spectrometer l.jpg

Linear Ion Trap Mass Spectrometer: 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


Rf fringing fields l.jpg

Axial Ion Ejection: Mass Spectrometer

Exit fringing fields couple radial/axial degrees of freedom of the trapped ions.

Excite ions radially to eject them axially.

RF Fringing Fields


Time averaged axial electric field l.jpg
Time Averaged Axial Electric Field Mass Spectrometer

Dehmelt approx.:

radial amplitude

fringing field

F. Londry, ASMS, 2002 .


Hybrid instrument with q3 linear ion trap ms l.jpg

Aux AC Mass Spectrometer

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



Slide11 l.jpg

Extraction Efficiency vs. Ejection q-Value Mass Spectrometer

(4x10-5 Torr)


Trapping extraction efficiencies l.jpg
Trapping & Extraction Efficiencies Mass Spectrometer

  • 5-inch long rod array:

    • Trapping efficiency: ~45%

      • 4x10-5 Torr background pressure

    • Extraction efficiency: 16-20%

      • q-value dependent

    • Overall efficiency: ~8%


Hybrid approach to product ion ms ms l.jpg

eV Mass Spectrometer

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.


Product ion scanning l.jpg
Product Ion Scanning Mass Spectrometer

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.


Slide15 l.jpg

Sensitivity Enhancements Mass Spectrometer

QqQ

Reserpine – Product Ion

Q1 Open Resolution

Enhanced Product Ion Scan

> 350x


Slide16 l.jpg

Sensitivity Enhancements—Reserpine Mass Spectrometer

QqQ

Q1 Open Resolution

Enhanced Product Ion Scan


Slide17 l.jpg

No Low Mass Cut-off Mass Spectrometer

Taurocholic Acid–

Product Ion

LCQ Deca – 45% CE

3 amu isolation width

Enhanced Prod Ion Scan – 75eV


Slide18 l.jpg

Resolution and Scan Speed: Reserpine Mass Spectrometer

4000 amu/sec

~0.55 amu wide

1000 amu/sec

~0.35 amu wide

250 amu/sec

~0.15 amu wide


Slide19 l.jpg

Mass Shift vs. Ejection q-Value Mass Spectrometer

3.5x10-5 Torr

103X Change of Ion Current


Slide20 l.jpg

Mass Shift vs. Input Ion Intensity Mass Spectrometer

q=0.86, m/z=609


Space charge effects l.jpg

D~ Mass Spectrometer0.02 amu

104x > ion current

Space Charge Effects

Q3 Space Charge Effects (3x10-5 Torr):


Rf dc quadrupole linear ion trap mass spectrometer l.jpg
RF/DC Quadrupole-Linear Ion Trap Mass Spectrometer 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


Future directions l.jpg
Future Directions Mass Spectrometer

  • 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.


Acknowledgments l.jpg
Acknowledgments Mass Spectrometer

  • Yves LeBlanc

  • Frank Londry

  • Bill Stott

  • Bruce Collings

  • John Vandermey


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