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FOURIER TRANSFORM MASS SPECTROMETRY

https://goo.gl/Vx3oGW

FT-ICR Theory – Ion Cyclotron Motion

• Inward directed Lorentz force causes ions to move in circular orbits about the magnetic field axis

Alan G. Marshall, Christopher L. Hendrickson, and George S. Jackson Encyclopedia of Analytical Chemistry, R.A. Meyers (Ed.), John Wiley & Sons Ltd, Chichester, 2000, pp. 11694–11728

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Ion cyclotron motion. Ions rotate in a plane perpendicular to the direction of a spatially uniform magnetic field,

Note that positive and negative ions orbit in opposite senses.

FT-ICR Theory – Ion Cyclotron Motion

X

Y

Z

c=qBm

FT-ICR TheoryFT-ICR Theory – Ion Cyclotron Motion

3

Once we make an ion, we move it into the center of the Magnet.

Then, we trap it before it can escape.

ION+

Electrostatic Barrier

From Primer 1998 Marshall.



ION+


Ion sees barrierand is turned back


4



ION+


“Gate” shut before the ion escapes




+ION

Ion is now trapped in the magnet.


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T T

Magnetic Field (B)

X

Y

Z

E

Axial Position

FT-ICR Theory - Ion Trapping

T T

Magnetic Field (B)

X

Y

Z

E

Axial Position


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T T

Magnetic Field (B)

X

Y

Z

E

Axial Position


vm = magnetron motionvc = cyclotron motionvt = trapping oscillations

Alan G. Marshall, Christopher L. Hendrickson, and George S. Jackson Encyclopedia of Analytical Chemistry, R.A. Meyers (Ed.), John Wiley & Sons Ltd, Chichester, 2000, pp. 11694–11728

FT-ICR Theory – Combined Ion Motion

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Time (ms)

8007006005004003002001000

Imag

e

0.05

0.04

0.03

0.02

0.01

0

-0.01

-0.02

-0.03

-0.04

-0.05

FT-ICR Theory - Excitation


X

Y

Z or Bo

Time

Am

pli

tud

e

Excitation Electrodes

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FT-ICR Theory Excitation

Alan G. Marshall, Christopher L. Hendrickson, and George S. Jackson Encyclopedia of Analytical Chemistry, R.A. Meyers (Ed.), John Wiley & Sons

Ltd, Chichester, 2000, pp. 11694–11728

Single Notch SWIFT Event (MS/MS)

100%

0%

Po

wer

Frequency

Freq CutoffBandwidth

End FrequencyStart Frequency

Data Count Affects Resolution

(Limited to < 512K)

SWIFT Excitation

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100%

0%

Po

wer

Frequency

SWIFT Excitation

IFT


X

Y

Z or Bo

Excitation ElectrodesTime

Am

pli

tud

e

10

SWIFT Excitation

m/z150014001300120011001000900800700

781780.5780.0779.5779.0778.5

m/z

781780.5780.0779.5779.0778.5

m/z

On -the -fly SWIFT isolation of a single

Isotope of Bovine Ubiquitin

11+

12+

10+

9+

8+

M+4 Isotope11+

FT-ICR Theory - Detection

X

Y

Z or Bo

11

Differential Amplifier

Time (ms)8007006005004003002001000

Imag

e C

urr

ent

0.05

0.04

0.03

0.02

0.01

0

-0.01

-0.02

-0.03

-0.04

-0.05

Time Domain Transient

Multiplex Detection in FT-ICR


Time (ms)8007006005004003002001000

Imag

e C

urr

ent

0.05

0.04

0.03

0.02

0.01

0

-0.01

-0.02

-0.03

-0.04

-0.05


Multiplex Detection in FT-ICR

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Signal Apodization in FT MS


Time (ms)8007006005004003002001000

Imag

e C

urr

ent

0.05

0.04

0.03

0.02

0.01

0

-0.01

-0.02

-0.03

-0.04

-0.05

Frequency (kHz)300250200150100500

Fourier Transform


Frequency Spectrum

Fourier Transforms in FT-ICR

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Mass Calibration in FT-ICR

Frequency (kHz)300250200150100500

Frequency Spectrum

m/z14001300120011001000900800700600500

mz

Af

= +BVt

f2

Mass Spectrum

Space Charge and Resolution in FT-ICR

T T

T T

m/z953.5953.0952.5952.0

953.5953.0952.5952.0m/z

LOW ION DENSITY

HIGH ION DENSITY

Detection Time(msec)

8006004002000

Detection Time(msec)

8006004002000

FT

FT

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Resolving PowerHighest Non-Coalesced MassScan Speed (LC/MS)Axialization Efficiency

Number of IonsTrapped Ion Upper Mass Limit 2D-FT Resolving PowerIon Trapping TimeIon Energy

34.7

7 9.411.5

15

25

0 5 10 15 20 25

3 4.7 7 9.411.5

15

25

Effect of Magnetic Field Strength

Field Strength (Tesla)

FT-ICR Experiment - Event Sequences

- Use a single mass analyzer but separate the mass analysis and ion isolation events in time

- Can perform many successive stages of MS (MSn)

Event Sequence

Ionization

Ion Transfer / Ion Trapping

Parent Ion Isolation

Parent Ion Fragmentation

Daughter Ion Detection

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(m/z)max(m/z)minm/z

Peak Capacity =m50%

(m/z)max - (m/z)min

m50%

Ultra-high Resolving Power

Separation Method

Maximum # of Components

MaximumPeak Capacity

TheoreticalPlates

HP-TLC 6 25 1,000

Isocratic LC 12 100 15,000

Gradient LC 17 200 60,000

HPLC 37 1,000 1,500,000

CE 37 1,000 1,500,000

Open Tubular GC 37 1,000 1,500,000

ESI FT-ICR MS 525 200,000 60,000,000,000

m/m50% > 200,000

200 < m/z < 1,000maverage +/- 0.25 Da Skip Prior Chemical Separation

and Identify Components by MS!

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)Ryan P. Rodgers, Alan G. Marshall, Petroleomics: Advanced Characterization of Petroleum-Derived Materials by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICRMS, Asphaltenes, Heavy Oils, and Petroleomics 2007, pp 63-93

)Ryan P. Rodgers, Alan G. Marshall, Petroleomics: Advanced Characterization of Petroleum-Derived Materials by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICRMS, Asphaltenes, Heavy Oils, and Petroleomics 2007, pp 63-93

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S. D.-H. Shi, C. L. Hendrickson, and A. G. Marshall Proc. Natl.

Acad. Sci. USA, 1998, 95, 11532–11537.

Isotopic Fine Structure

Resolving power

M M50%

= 8,000,000

Anal Chem. 2011 November 15; 83(22): 8391–8395. doi:10.1021/ac202429c.

Unit Mass Baseline Resolution for an Intact 148 kDa Therapeutic Monoclonal Antibody by FT-ICR Mass Spectrometry

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J. Am. Soc. Mass Spectrom. (2015) 26:1626Y1632

Single-scan electrospray FT-ICR mass spectrum of the isolated 48+ charge state of bovine serum albumin

Principle of Trapping in the Orbitrap

Orbital trapsKingdon (1923)

• The Orbitrap is an ion trap – but there are no RF or magnet fields!

• Moving ions are trapped around an electrode

- Electrostatic attraction is compensated by centrifugal force arising from the initial tangential velocity

• Potential barriers created by end-electrodes confine the ions axially

• One can control the frequencies of oscillations (especially the axial ones) by shaping the electrodes appropriately

• Thus we arrive at …

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Orbitrap - Electrostatic Field Based Mass Analyser

z

φ

r

)/ln(2/2

),( 222mm RrRrz

kzrU

Korsunskii M.I., Basakutsa V.A. Sov. Physics-Tech. Phys. 1958; 3: 1396.Knight R.D. Appl.Phys.Lett. 1981, 38: 221.Gall L.N.,Golikov Y.K.,Aleksandrov M.L.,Pechalina Y.E.,Holin N.A. SU Pat. 1247973, 1986.

• Only an axial frequency does not depend on initial energy, angle, and position of ions, so it can be used for mass analysis

• The axial oscillation frequency follows the formula

zm

k

/

Ion Motion in Orbitrap

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Ions of Different m/z in Orbitrap

• Large ion capacity -stacking the rings

• Fourier transform needed to obtain individual frequencies of ions of different m/z

How Big Is the Orbitrap?

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Getting Ions into the Orbitrap

• The “ideal Kingdon” field has been known since 1950’s, but not used in MS. Why?There is a catch

– how to get ions into it ?

• Ions coming from the outside into a static electric field will zoom past, like a comet from the outer space flies through a solar system

• The catch: The field must not be static when ions come in!

– A potential barrier stopping the ions before they reach an electrode can be created by lowering the central electrode voltage while ions are still entering

• Thus we arrive at the principle of

Electrodynamic Squeezing

A.A. Makarov, Anal. Chem. 2000, 72: 1156-1162.A.A. Makarov, US Pat. 5,886,346, 1999.A.A. Makarov et al., US Pat. 6,872,938, 2005.

Curved Linear Trap (C-trap) for ‘Fast’ Injection

Push

Trap

Pull

Lenses

Orbitrap

Gate

Deflector

• Ions are stored and cooled in the RF-only C-trap

• After trapping the RF is ramped down and DC voltages are applied to the rods, creating a field across the trap that ejects along lines converging to the pole of curvature (which coincides with the orbitrap entrance). As ions enter the orbitrap, they are picked up and squeezed by its electric field

• As the result, ions stay concentrated (within 1 mm3) only for a very short time, so space charge effects do not have time to develop

• Now we can interface the orbitrap to whatever we want!

A.A. Makarov et al., US Pat. 6,872,938, 2005.A. Kholomeev et al., WO05/124821, 2005.

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Dependence of resolving power on m/z for the following analyzers (all data are shown for a 0.76 s scan): (i) standard trap (magnitude mode, 3.5 kV on central electrode), (ii) compact high-field trap (eFT, 3.5 kV on central electrode), (iii) FTICR (magnitude mode, 15 T), (iv) FTICR (absorption mode, 15 T).

Comparison of Resolving Power as a function of mass for Orbitrap and ICR

Anal. Chem. 2013, 85, 5288−5296

Hybrid Orbitrap XL

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Hybrid Orbitrap Elite

Hybrid Orbitrap Fusion

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Highly Parallel Data Acquisition

ControlB3a #4869 RT: 41.56 AV: 1 NL: 7.39E6T: FTMS + p NSI Full ms [465.00-1600.00]

500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Re

lativ

e A

bu

nd

an

ce

600.9776

804.3450

558.7548

532.2505

649.9460

699.3472897.9816

716.0311956.8159

849.8573 974.9185 1116.5020

Parallel Detection in Orbitrap and Linear Ion Trap

• Total cycle is 2.4 seconds• 1 High resolution scan • 5 ion trap MS/MS in parallel

RT: 41.56High resolutionFull scan # 4869

ControlB3a #4870 RT: 41.57 AV: 1 NL: 7.16E3T: ITMS + c NSI d Full ms2 [email protected] [150.00-1810.00]

200 400 600 800 1000 1200 1400 1600 1800

m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Re

lativ

e A

bu

nd

an

ce

437.9462

542.7487

590.2733

983.4816

776.4982

623.5060

301.24471084.6279

1171.8290

RT: 41.57MS/MS of m/z 598.6Scan # 4870


400 600 800 1000 1200 1400 1600 1800m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bu

ndan

ce

1092.6033

1409.7291

856.3868

539.2245

1294.7877965.7724

1223.7373

654.2495 757.5266 1801.9797

1513.5245436.2499

1674.7556393.1896


200 400 600 800 1000 1200 1400 1600

m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Re

lativ

e A

bu

nd

an

ce

535.5252

690.1100

490.3550

575.8568

450.8616361.2963

747.4839

330.2767262.1056

900.6165 1022.6853234.2242

1088.7388

RT: 41.58MS/MS of m/z 547.3Scan # 4871

RT: 41.58MS/MS of m/z 777.4Scan # 4872

RT: 41.59MS/MS of m/z 974.9Scan # 4873

RT: 41.60MS/MS of m/z 1116.5Scan # 4874


200 250 300 350 400 450 500 550 600 650 700 750

m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Re

lativ

e A

bu

nd

an

ce

701.4880

592.5975

400.3238

729.5197

767.4117

654.3235

354.2529 683.1174371.1810

309.1429 547.4052512.5754469.5364252.0748


400 600 800 1000 1200 1400 1600 1800m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bu

ndan

ce

1092.6033

1409.7291

856.3868

539.2245

1294.7877965.7724

1223.7373

654.2495 757.5266 1801.9797

1513.5245436.2499

1674.7556393.1896

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January 1, 2014 Molecular & Cellular Proteomics, 13, 339-347.


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Rate of protein identifications as a function of mass spectrometer scan rate forselected large-scale yeast proteome analyses over the past decade. Each data point isannotated with the year, corresponding author, type of MS system used, and referencenumber.


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