Its On Mass Spectrometry Basic principle

1. A.S.M. Asadur Rahman
ID: 121410 ;Sess:2012-2013
Department of Chemistry
Comilla University
Presentation On
Mass Spectrometry Theory
&
Instrumentation 31-Oct-17 1

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3. A molecular ion results when one electron is removed from the parent
molecule of the substance.
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Theory of Mass Spectrometry

4. The Mass Spectrometry is designed to perform three
basic functions—
 To vaporize compounds of varying volatility.
 To produce ions from the neutral compounds in the vapour phase.
 To separate ions according to their mass over charge ratio & to record
them.
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Theory of Mass Spectrometry

5. Mass Spectrometer Schematic
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Inlet
Ion
Source
Mass
Filter Detector
Data
System
High Vacuum System
Turbo pumps
Diffusion pumps
Rough pumps
Rotary pumps
Sample Plate
Target
HPLC
GC
Solids probe
MALDI
ESI
IonSpray
FAB
LSIMS
EI/CI
TOF
Quadrupole
Ion Trap
Mag. Sector
FTMS
Microch plate
Electron Mult.
Hybrid Detec.
PC’s
UNIX
Mac

6. Instrumentation
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There are four key stages in the process for Mass Spectrometry.
1) Ionization 2) Acceleration 3) Deflection 4) Detection

7. Different Ionization Methods…….
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Ionization
• Electron Impact (EI - Hard method)
– small molecules, 1-1000 Daltons, structure
• Fast Atom Bombardment (FAB – Semi-hard)
– peptides, sugars, up to 6000 Daltons
• Electrospray Ionization (ESI - Soft)
– peptides, proteins, up to 200,000 Daltons
• Matrix Assisted Laser Desorption (MALDI-Soft)
– peptides, proteins, DNA, up to 500 kD

8. Ionization
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Electron impact Ionization is the
most common type of ionization.
• The sample is bombarded by
electrons which come from a
heated filament.
• The electrons run in a stream
between the cathode and anode.
• When the sample passes through
the electron stream, the high
energy electrons in the stream
knock electrons out of the sample
to form ions.

9. The Bombardment of electron may result in the following types
of ions………..
𝑨𝑩(𝒈) + 𝒆 → 𝑨𝑩∗
+ 𝒆
→ 𝑨𝑩+ + 𝟐𝒆 ( Most probable )
→ 𝑨𝑩+𝒏
+ 𝒏 + 𝟏 𝒆 ( Least Probable )
→ 𝑨+
+ 𝑩−
+ 𝒆
→ 𝑨+
+ 𝑩 + 𝟐𝒆
→ 𝑨𝑩−
( Electron capture-less probable)
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Ionization

10. Acceleration
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• Acceleration is a simple step where
the ions are placed between a set of
charges parallel plates.
• The ions will then be repelled by one
plate and attracted to the other.
• There is a slit cut in the plate which
the ions are attracted to. the force of
attraction and repulsion forces the
ions through the slit at an
accelerated rate.
• The speed of acceleration can be
adjusted by changing the charge on
the plates.

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• Magnetic Sector Analyzer (MSA)
– High resolution, exact mass, original MA
• Quadruple Analyzer (Q)
– Low (1 amu) resolution, fast, cheap
• Time-of-Flight Analyzer (TOF)
– No upper m/z limit, high throughput
• Ion Trap Mass Analyzer (QSTAR)
– Good resolution, all-in-one mass analyzer
• Ion Cyclotron Resonance (FT-ICR)
– Highest resolution, exact mass, costly
Deflection or Mass
Analyzer

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Deflection or Mass
Analyzer
•Ions are deflected by the magnetic
field surrounding the instrument which
depends on the mass and charge of
the ions.
Ion stream C: The heavier ions are
deflected the least.
Ion Stream B: Correct mass ions and
charge travel to the detector.
Ion Stream A: The lightest ions are
deflected the most.

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14. Thanks to all………
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