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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
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