Presentation on mass spectroscopy

Principle, theory and instrumentation of Mass spectrometry

1. Mass Spectrometry
Presented by,
Ms.Smita P.Shelke,
Assistant Professor
Gokhale Education Society’s
Sir Dr M.S. Gosavi College Of Pharmaceutical Education & Research
Prin.T.A.Kulkarni Vidyanagar, Nashik-422005
India (Maharashtra). Ph No. 0253 2232799.

2. Mass Spectrometry
Used by Three Ways:-
For structural elucidation of ionic
fragments
Measurement of relative molecular
mass: molecular formula
Comparison and identification of
known compounds

3. Theory of MS
MS separates individual atoms because of differences
in their masses
consider M is a molecule focused with beam of e
-
M + e
-
M+ + 2e
-
ions accelerated with voltage V,
now energy of each particle = kinetic energy
½ mv
2
=eV………………………..(1)
•v= Velocity of particle
•m= Mass of particle
•e= Charge on electron
•V= Voltage

4. Now charge particles enter a magnetic field H, field
attracts the particle and they move in a circle around
it with a force Hev
•However particles have centrifugal force mv
2
/r
•When these two forces are equal :molecule start
moving: i.e.
mv
2
/r = Hev………………..(2)
•v= Velocity of particle
•m= Mass of particle
•r= Radius of circle
•H= magnetic field
•e= Charge on electron

5. m/e = H
2
r
2
/ 2V…………..(3)
•m/e= mass to charge ratio is depends on H, V and r
As e, V and H are constant
•m= mass is depends on r

6. Flow of Ions in Mass Spectroscope

7. INSTRUMENTATION
OF
MASS SPECTROSCOPY

8. Classical Mass Spectroscope

9. Instrument of MS

10. Schmatics of MS instrument

11. Basic Components of MS Instrument
Sample Inlet System
Ion Source / Ionization Chamber
Electrostatic Accelerating System
Ion Seperator / Analyser
Magnetic Field
Ion Collector
Vacuum System

12. Sample Inlet Systems in MS
Sample must be in vapourphase
Less volatile heated before injection in
ampoule.
Smpleswith less vapourpressure are with
Probe

13. IONIZATION METHODS
1. Gas Phase
 Electron Impact
 Chemical Ionization
 Field Ionization
2. Desorption Phase
Field desorption
Electro spray Ionization
MALDI
FAB
Thermo spray Ionization

14. Electron Impact (EI)
A high energy electron beam dislodges an
electron from a
sample molecule to produce a positive ion
M + e → M+. + 2e
M= analyte molecule, M+.= Radical ion

15. Schematics of EI

16. Benefits
owell-understood
ocan be applied to virtually all volatile
compounds
oreproducible mass spectra
ofragmentation provides structural
information
olibraries of mass spectra can be searched
for EI mass spectral "fingerprint"

17. Chemical Ionization (CI)
Gaseous atoms of the sample are
bambarded with reagent gas.
Reagent gas-methane gas
All of the primary ions of methane
react rapidly with methane (at virtually
every collision) to give product ions

18. Mechanism of Methane gas
Collison of methane to produce ions
CH
4
+
+ CH
4--> CH
5
+
+ CH
3
CH
3
+
+ CH
4--> C
2H
5
+
+ H
2
Interaction of ions with molecule M
MH + C
2H
5
+
--> MH
2
+
+ C
2H
4
MH + C
2H
5
+
--> M
+
+ C
2H
6

19. Field Ionization (FI) Soft Ionization
Emitters of Tungsten wireused on which
microscopic dendrites / emmittersare
formed (by Pyrolysis)
The mechanism of ionisation-when a
molecule is subjected to a very high
electric field, ( > 10*9 volts/metre), a
valence electron tunnels through the
potential barrier and is removed from the
molecule. The resulting ion is therefore a
radical, M+.

20. carbon emitters and silicon emitters.
Silicon emittersare robust, relatively
inexpensive, and they can handle a higher
current for field desorption.
Carbon emittersare more expensive, but
they can provide about an order of
magnitude better sensitivity than silicon
emitters.

21. Carbon Dendrimers

22. Desorption Field Ionization
Field desorption ionization are soft
ionization methods that tend to
produce mass spectra with little or no
fragment-ion content.
Benefits
simple mass spectra, typically one
molecular or molecular-like ionic
species per compound.

23. little or no chemical background
works well for small organic molecules,
many organometallics, low molecules -
polymers and some petrochemical
fractions
Limitations
sensitive to alkali metal contamination and
sample overloading
emitter is relatively fragile
relatively slow analysis as the emit
the sample must be thermally volatile

24. Electrospray Ionization
The sample solution is sprayed across a
high potential difference (a few kilovolts)
from a needle into an orificein the
interface. Heat and gas flows are used to
desolvate the ions existing in the sample
solution.

25. Electrospray Ionization

26. Advantages of ESI
•good for charged, polar or basic
compounds
•permits the detection of high-mass
compounds at mass-to-charge ratios that
are easily
•best method for analyzing multiply
charged compound
•very low chemical background leads to
excellent detection limits
•compatible with MS/MS methods

27. Matrix Assisted Laser Desorption
Ionization (MALDI)
The analyte is dissolved in a solution
containing an excess of a matrix such as
sinapinic acid or dihydroxybenzoic acid
that has a chromophore that absorbs at
the laser wavelength.

28. Matrix Assisted Laser Desorption
Ionization (MALDI)
The matrix absorbs the energy from the
laser pulse and produces a plasma that
results in vaporization and ionization of the
analyte.

29. Matrix Assisted Laser Desorption
Ionization (MALDI)

30. Advantages of MALDI
rapid and convenient molecular weight
determination
Limitations of MALDI
MS/MS difficult
requires a mass analyzer that is
compatible with pulsed ionization
techniques
not easily compatible with LC/MS

31. Fast Atom Bombardment (FAB)
The analyte is dissolved in a liquid matrix
such as glycerol, thioglycerol, m-
nitrobenzyl alcohol, or diethanolamine and
a small amount (about 1 microliter) is
placed on a target.

32. Fast Atom Bombardment (FAB)
The target is bombarded with a fast atom
beam (for example, 6 keV xenon atoms)
that desorb molecular-like ions and
fragments from the analyte.
Cluster ions from the liquid matrix are also
desorbed and produce a chemical
background that varies with the matrix
used.

33. Fast Atom Bombardment (FAB)

34. Mass analyzers
OR
Separators

35. Mass analyzers / Seperators
1.Sector analysers
Single focusing
Double focusing
2. Quadrupole analyser
Mass filter
Ion trap/ Ion storage
3. Time of Flight (TOF)
4. FT-Ion Cyclotron Resonance (FT-ICR)

36. Mass analyzers / Seperators
1.Sector analysers:
uses an electric and/or magnetic field to affect
the path and/or velocityof the chargedparticles .
bend the trajectories of the ions as they pass
through the mass analyzer, according to their
mass-to-charge ratios.
deflecting the more charged and faster-moving,
lighter ions more.

37. 1.1 Single Focusing Sector Analyser

38. 1.2 Double Focusing
Mass spectrometerthat incorporates a
magnetic sectorand an electric sector
connected in series in such a way that
ions with the same m/zbut with
distributions in both the direction.

39. 1.2 Double Focusing

40. 2.1 Quadrupole analyser : Mass filter
A quadrupole mass filter consists of four
parallel metal rods
Two opposite rods have an applied
potential
The applied voltages affect the trajectory
of ions traveling between the four rods.
only ions of a certain mass-to-charge ratio
pass through the quadrupole filter.

41. Quadrupole analyser : Mass filter

42. Quadrupole analyser : Ion Trap
an ion trapuses constant DCand radio
frequency(RF) oscillating ACelectric
fieldsto trap ions.
It is commonly used as a component of
a mass spectrometer.

43. Quadrupole analyser : Ion Trap

44. 3. Time Of Flight (TOF)
an ion's mass-to-charge ratiois
determined via a time measurement.
Ions are accelerated by an electric fieldof
known strength.
This acceleration results in an ion having
the same kinetic energy.
The velocity of the ion depends on the
mass-to-charge ratio.
The time that it takes for the particle to
reach a detector at a known distance is
measured.

45. 3. Time Of Flight (TOF)

46. 3. FT-Ion Cyclotron resonance (FT-ICR)
the mass-to-charge ratio(m/z) of ions
based on the cyclotron frequencyof the
ions in a fixed magnetic field.
The ions are trapped in a Penning trap(a
magnetic field with electric trapping plates)
where they are excited by rf
After the excitation field is removed, the
ions are rotating at their cyclotron
frequency in phase (as a "packet" of ions).

47. FT-Ion Cyclotron resonance (FT-ICR)
These ions induce a charge on a pair of
electrodes as the packets of ions pass
close to them.
Theresultingsignaliscalledafree
inductiondecay(FID),transientor
interferogramthatconsistsofa
superpositionofsinewaves.
Theusefulsignalisextractedfromthis
databyperformingaFouriertransform

48. ION CYCLOTRON

49. FT-Ion Cyclotron resonance (FT-ICR)

50. Tandem Mass Spectroscopy MS-MS
Multiple stages of mass analysis separation
can be accomplished with individual mass
spectrometer.
Elements separated in space or using a
single mass spectrometer with the MS
steps separator.

51. Tandem Mass Spectroscopy MS-MS

52. Methods of Ion Detection / Ion
detectiors
Mass analysis -i.e. the separation of
bunches or streams of ions according to
their individual mass-to-charge (m/z) ratio.
The most common types of ion detector
used in modern instruments:
1. The Faraday Cup or Cylinder
2. The Electron Multiplier
3. The Photomultiplier or
Scintillation Counter.

53. 1. The Faraday Cup or Cylinder
The basic principle is that the incident ion
strikes the dynode surface, which emits
electrons and induces a current which is
amplified and recorded.
The dynode electrode is made ofa
secondary emitting material like CsSb,
GaP or BeO.
The Faraday cup is very robust.

54. 1. The Faraday Cup or Cylinder

55. 2. The Electron Multiplier
A Faraday cup uses one dynode, it has
series of dynodes maintained at increasing
potentials resulting in a series of
amplifications.
Their are two types of electron multiplier

56. 2. The Electron Multiplier

57. 3. The Photomultiplier or
Scintillation Counter.
The ions initially strike a dynode which
results in electron emission.
These electrons then strike a phosphorous
screen which in turn releases a burst of
photons.
The photons then pass into the multiplier
where amplification occurs in a cascade

58. 3. The Photomultiplier or
Scintillation Counter.

59. Interpretation of MS Spectrum
The mass spectrum produced will usually
be presented as a vertical bar graph, in
which each bar represents an ion having a
specific mass-to-charge ratio (m/z) and the
length of the bar indicates the relative
abundance of the ion.

61. Sector Analyser

62. QUADRUPOLE
and 27.9949 Daltons, respectively
2
.

63. Time of Flight

64. Types of Ion in MS / Interpertation
Mass Spectrum

65. Gas Chromatograph with MS

66. Applications of Mass Spectroscopy