Mass Analyzers

• Double Focusing Magnetic Sector

• Quadrupole Mass Filter

• Quadrupole Ion Trap

• Linear Time-of-Flight (TOF)

• Reflectron TOF

• Fourier Transform Ion Cyclotron Resonance (FT-ICR-MS)

Mass Analyzers• Resolution

– R = m / Δm

• Accuracy/Precision– mass measurement accuracy/reproducibility

• Transmission– % of ions allowed through the analyzer

• Mass Range– Highest m/z that can be analyzed

• Scan Speed– How many spectra per unit of time

Effect of Increased Resolution

Gastric Inhibitory PeptideC225H341N59O66SMW: 4957

Pulmonary SurfactantC917H1473N235O268S11

MW: 20417

Spectroscopy 2004, 19, 34-40.

Double-Focusing Magnetic Sector

Double-Focusing Magnetic SectorMagnetic Sector

mq

r2B2

2V=

B = magnetic field strengthr = radius of curvature in magnetic fieldV = accelerating voltagem = ion massq = ion charge

All ions of the same m/z will have the same radius

Only if the Ion kinetic energy is constant

Double-Focusing Magnetic SectorElectric Sector

r 2Ek

qE=

Ek = ion kinetic energyr = radius of curvature in electric fieldE = magnitude of electric fieldq = ion charge

All ions exiting the electric sector have the same kinetic energy

Magnetic Sector

• Typically a voltage of 5-10kV is used to accelerate ions

• To obtain a full spectrum, magnetic field is scanned

• To obtain a HR scan, voltage is scanned at constant magnetic field

• To gain maximum sensitivity at one mass SIM scan is done– B and E are constant for one or more

masses

Quadrupole Mass Filter

http://www.asms.org

Quadrupole

E = U - Vcos(2πνt)

E = potential applied to the rodsU = DC potentialV = RF amplitudeν = RF frequencyt = time

Quadrupole is scanned at a constant U/V

Quadrupole

• Typically U varies from 500-2000 V

• V varies from 0 - 3000V (-3000 to +3000)

• Scanning U/V at a fixed ratio gives a full scan– Higher values of U/V give higher resolution

• RF only (U=0) transmits all ions

• Higher sensitivity through SIM scan– Jumping to specific points on the U/V line

MS/MS with multiple quadrupoles

1.Product ion scanESI and/or LC-MS

2. Precursor ion scanEI or CI and GC-MS

3. Neutral loss scanEI and CI

http://www.chm.bris.ac.uk/ms/theory/tandem-ms.html

Quadrupole Ion Trap

• Ions are injected into the trap and all ions are trapped

• RF and DC are scanned to sequentially eject ions for detection

• Specific ions can be trapped while others are ejected

• Ion velocity can be increased to induced fragmentation

Quadrupole Ion Trap

http://www.chm.bris.ac.uk/ms/theory/qit-massspec.html

Time-of-Flight (TOF)

mv2

2zVs=

Ek = kinetic energyv = ion velocityd = flight distancet = flight timeVs = accelerating voltagem = ion massq = ion charge

All ions of the same m/z will have the same flight time

Only if the Ion kinetic energy is constant

= Ekdt

= v t2 =mz

d2

2Vs

TOF

• Ions are accelerated with 5-35 kV

• Space focusing of source ions is accomplished by delayed extraction

• An electrostatic analyzer (reflectron) is used correct for kinetic energy spread

Reflectron Time-of-Flight

http://www.chm.bris.ac.uk/ms/theory/tof-massspec.html

Reflectron Time-of-Flight (ESI-TOF)

Courtesy Bruker Datonics BioTOF user’s Manual

FT-ICR-MSv

2πrf=

B = magnetic field strengthv = ion velocityf = orbital frequencym = ion massq = ion charger= orbital radius

At constant B, orbital frequency is inversely related to m/z

Frequency is independent of kinetic energy

qvB =mv2

rvr

2πf==qB

2πmCentripital

ForceCircular

Pathr and v drop out

FT-ICR-MS• Ions are all trapped radially by a

magnetic field (typically 3-15 T)

• Axial trapping by DC potential

• Ion radius is increased by RF pulse– also brings orbits into phase

• Orbiting ions induce RF current in receiver plates– Image current is a composite of all

frequences in time domain

• FFT gives frequency (mass) spectrum

FT-ICR-MSActively shielded magnet

analyzer stage

transfer stagesource chamberESI source

ESI needle(atmosphere)

capillary

ionguide

500 L/secturbo pump10-10 mbar

500 L/secturbo pump10-6 mbar

70 L/secturbo pump10-8 mbar

250 L/secturbo-dragpump10-4 mbar

5 L/secrotary vane10-1 mbar

cell

FT-ICR-MS

1200 1400 1600 1800 m/z

Δm = 0.01933 a.u.1/Δm = 51.7308 a.u.

mass = 64428 a.u.

1278.3 1278.8 m/z

52+52+

52+52+

60+60+36+36+

Electrospray: Broadband Spectrum of Bovine SerumAlbumin (66kDa) 7.0T Actively Shielded Magnet

FT-ICR-MSElectrospray: Deconvoluted Spectrum of BovineSerum Albumin (66kDa) 7.0T Actively Shielded Magnet

66410 66430 66450 m/z

Δm = 1.004 a.u.

Mass Analyzers: Performance and Price

Spectroscopy 2004, 19, 34-40.

Ion DetectorsElectron Multiplier

http://www.chm.bris.ac.uk/ms/theory/detection.html

Ion Detectors

http://www.chm.bris.ac.uk/ms/theory/detection.html

MS for Chemical ImagingTOF-SIMS imaging

+

cold stage

extractionlens

extractionlens

blanking aperture

secondary ions

retardreflect

reflectrondetector

Primary Ion Source

Tof SIMS Imaging

Courtesy of Mike Kurczy, Winograd Group, Penn State University

MASS SPEC IMAGING

Courtesy of Mike Kurczy, Winograd Group, Penn State University

Application of TOF-SIMS imaging to biology

Membrane lipid heterogeneity during tetrahymena mating

Membrane lipid heterogeneity during tetrahymena mating

Science 2004, 305, 71

Membrane lipid heterogeneity during tetrahymena mating

m/z = 69 m/z = 184

Science 2004, 305, 71

Membrane lipid heterogeneity during tetrahymena mating

PC is depleted in mating region

What lipid is enriched?

Should be “cone shaped”

Science 2004, 305, 71

Membrane lipid heterogeneity during tetrahymena mating

m/z = 126

Science 2004, 305, 71

Membrane lipid heterogeneity during tetrahymena mating

Science 2004, 305, 71