Ionization and Mass Analyzers
description
Transcript of Ionization and Mass Analyzers
Ionization and Mass Analyzers• Ionizations
– Electron Ionization - “hard” – Chemical Ionization - “soft”– MALDI - desorption– FAB - desorption– Laser Post Ionization - increase signal!– Ion Bombardment (SIMS) - soft or hard
• Depends on ion fluence
• Mass Analyzers– Analyze all mass/charge
• Time-of-flight– Pre- Select Ions
• Quadropole• Magnetic or Electric Sectors
Electron Ionization
• Molecule + e- molecule+ + 2e-
• Four electromagnetic poles• Rapidly oscillating field• If mass of ion and frequency of oscillation are comparable
then the ion will oscillate towards the detector and be measured
• A certain mass range can be selected depending on the pole diameter
Quadropole Mass Analyzer
Electrostatic and Magnetic Sectors
http://www.cea.com/cai/simsinst/m_anal.htm
22
2r
V
B
z
m
B = strength of magnetic field
V = ion accelerating voltage
r = radius of ion curvature
m = mass of ion
z = charge of ion
focusmass
separate
M = 1-50 (change by changing B)
Secondary Ion Mass Spectrometry“Ionization”
Static SIMS = < 1 x 1013 ions/cm2
Ga+
-+e-
10 ion
20 particles
Time-of-Flight Analyzer
2
2
2
2
2
2
1
2
1
d
teV
z
m
t
dmzeV
mvzeVd
Field Free Region
+V
M+
MCPdetector
-V
V = stage voltaged = length of field free regionV = voltage of detector
e = charge on an electron1.6 x 10-19 C
t = time for ion to reach detectorm = massv = velocity
Sam
ple
Sam
ple
TOF-SIMS InstrumentTOF-SIMS Instrument
Laser Postionization (LPI)Laser Postionization (LPI)
Postionization parametersPostionization parameters: 800 nm, 150 fs laser pulses, 8.5 x 1012 W/cm2 power density
Laser Beam
TOF-SIMS Molecule-Specific Imaging
molecule-specific image
Si+
Si+
Cu+
Cu+
Ag+
Ag+
m/z, +ions
total ion image
0 12 24 36 48 60 72 84 96 108 1200
1000
2000
3000
4000
5000
570 µm x 570 µm
Inte
nsity
copper grid affixed to silicon substrate with silver paste
Ion Gun
x
y
TOF-SIMS Identification of Plasma Membrane Lipids
m/z 369
OH
cholesterolm/z 385 (M-H)+
DPPE – dipalmitoylphosphatidylethanolamine
m/z 552m/z 142+2H** **
m/z 682 (M+H)+
O
O O
H
O
O
P
O
O
H3N
O
+ --
C. M. McQuaw; A. G. Sostarecz et. al. Langmuir 2005.
250
µm
x 2
50 µ
m
Are there Lipid Domains in the Inner Leaflet of the Membrane?
Total Ion DPPE/CholesterolTotal Ion DPPE/Cholesterol
-
O
O O
H
O
O
P
O
O
H3N
O
+552552
Cholesterol
cholesterolcholesterol
DPPE
DPPEDPPE
Inte
nsity
Inte
nsity
A. G. Sostarecz; C. M. McQuaw et. al. J. Am. Chem. Soc. 2004.
Au
Multi-Isotope Imaging Mass Spectrometry
endothelial cell
Image from Claude LecheneImage from Claude LecheneHarvard Medical SchoolHarvard Medical School
1414NN
nucleusnucleus lamellipodialamellipodia
Atomic Mass ImagesAtomic Mass Images
MIMS is a Secondary Ion Mass Spectrometry Technique
http://www.cea.com/cai/simsinst/m_anal.htm
22
2r
V
B
z
m
B = strength of magnetic field
V = ion accelerating voltage
r = radius of ion curvature
m = mass of ion
z = charge of ion
focusmass
separate
M = 1-50 (change by changing B)
-+e-
10 ion
20 particles
MIMS uses an Electrostatic and Magnetic Sector Mass Analyzer
*** MIMS analysis is performed as a collaborative project with Dr. Claude Lechene at the National Resource for Imaging Mass Spectrometry at Harvard Medical School
focusfocus mass separatemass separate
ion 1ion 1
Image from Claude Lechene
84 %84 %
16 %16 %
1414NN