By; Sowmya B U (Student) Under the Guidance; Mrs. Nethravathi P C Department of Studies and Research in Organic Chemistry Tumkur University Tumakuru.

1. Department of Studies and Research in Organic Chemistry
Seminar presentation on
“Instrumentation of Mass Spectrometry”
By
Ms. Sowmya B U
Register number: 19POC131
II MSc, IV Sem
Department of Studies and Research in Organic Chemistry
Tumkur University, Tumakuru
Under the guidance
Mrs. Nethravathi P C
Department of Studies and Research in Organic Chemistry
Tumkur University, Tumakuru
Submitted to
Dr. Aruna Kumar D B
The Coordinator
Department of Studies and Research in Organic Chemistry
Tumkur University, Tumakuru
2020-21
TUMKUR UNIVERSITY

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CONTENTS
Introduction to Mass Spectrometry
Basic Principles of Mass Spectrometry
Mass Spectrometer Overview
Major components of Mass Spectrometer
Conclusion
References
Sample Inlet
Ion Source
Mass Analyzer
Detector, Amplifier and Recorder
Data System
1
2
3
4
5
6
A
B
C
D
E

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1. Introduction to Mass Spectrometry
Mass spectrometry is unlike the other spectroscopic techniques that it does not measure
the interaction of molecules with the spectrum of energies found in the electromagnetic
spectrum, but the output from the instrument has all other spectroscopic
characteristics, in showing an array of signals corresponding to a spectrum of energies;
to highlight this distinction , the name mass spectrometry is preferred.
The fundamental principles date to the late 1890s when
J. J. Thomson determined the mass-to-charge ratio of the
electron, and Wien studied magnetic deflection of anode rays
and determined the rays were positively charged. Each man
was honored with the Nobel Prize (Thomson in 1906 and
Wien in 1911) for their efforts.
In 1912–1913, J. J. Thomson studied the mass spectra of
atmospheric gases and used a mass spectrum to demonstrate
the existence of neon-22 in a sample of neon-20, thereby
establishing that elements could have isotopes. The earliest
mass spectrometer, as we know it today, was built by
A. J. Dempster in 1918.
J. J. Thomson
(1856-1940)

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2. Basic Principles of Mass Spectrometry
The first step in the mass spectrometric analysis of compounds is the production of gas-
phase ions (molecular ion) of the compound, for example by electron ionization;
M + e- → M•+ + 2e-
This molecular ion normally undergoes fragmentations. Because it is a radical cation
with an odd number of electrons, it can fragment to give either a radical and an ion
with an even number of electrons or a molecule and a new radical cation.
m1
+ + m•
M•+
m1
•+ + m2
All these ions are separated in the mass spectrometer according to their mass-to-charge
ratio and are detected in proportion to their abundance. The plot of ion abundance
versus mass-to-charge ratio will gives the mass spectra.
(Molecular ions having lifetime of at least 10-5 sec will reach the detector without
breaking into fragments).

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B
D
A
C E
H
J
K
L
F
G
I
A. Sample inlet
B. Sample vapourization chamber
C. Heating coil
D. Ionization chamber
E. Electron source
F. Neutral ions collector
G. Accelerating plates(a , b and c)
H. Magnet
I. Mass analyzer
J. Detector
K. Amplifier
L. Recorder
3. Mass Spectrometer Overview

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Flow Chart
Sample inlet
(Sample insertion)
Sample
vapourization
chamber
(Vapourization)
Ionization chamber
(Ionization and
Fragmentation)
(Acceleration)
Recorder
Amplifier
(Amplification)
Detector
(Detection)
Mass analyzer
(Mass separation)
Magnetic analyzer
(Deflection)
Mass spectrometer

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4. Major Components of Mass Spectrometer
A. Sample Inlet
A sample inlet system provides stream of
molecules. A sample studied by mass
spectrometry may be a gas, a liquid, or a
solid. The sample is introduced into a
larger reservoir from which the gaseous
molecules (from vaporization using
heating coils) can be drawn into the
ionization chamber.
Handling of gas sample:
It involves the transfer
of sample containers of
known volume coupled
to mercury manometer.
Introduction of liquid
sample:
The sample is converted
into gaseous state then
injected by using a
micropipette to a sintered
glass disk under a layer of
molten gallium.
Introduction of solid
sample:
Samples with lower vapor
pressures are inserted
directly into the ionization
chamber on the end of a
probe, and their
volatilization is controlled
by heating the probe tip .
Sample introduction methods:
Gas Chromatography
Direct infusion
Liquid chromatography
Capillary electrophoresis
Direct ionization
Direct insertion probe

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B. Ion Source
The several methods available for inducing the
ionization of organic compounds but electron
bombardment is routinely used . Organic molecules
react on electron bombardment in two ways: either an
electron is captured by the molecule , giving a radical
anion, or an electron is removed from the molecule,
giving a radical cation.
Most organic molecules form molecular ions (M•+) when
the energy of the electron beam reaches 10-15 eV (≈ 103
kJ mol-I). While this minimum ionization potential is of
great theoretical importance, fragmentation of the
molecular ion only reaches substantial proportions at
higher bombardment energies, and 70 eV (≈ 6 X 103 kJ
mol") is used for most organic work .
When the molecular ions have been generated in the
ionization chamber, they are expelled electrostatically by
means of a low positive potential on a repeller plate a in
the chamber. Once out, they are accelerated down the
ion tube by the much higher potential between the
accelerating plates b and c.

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C. Mass Analyzer
Seperation of the ions in the analyzer:
In a magnetic analyzer, ions are separated on the basis of m/z values. The kinetic energy, E of an ion
of mass m travelling with velocity v is given by ; E =1/2mv2.
The potential energy of an ion of charge z being repelled by an electrostatic field of voltage V is zV.
When the ion is repelled, the potential energy, zV is converted into the kinetic energy, 1/2mv2 so
that;
zV = 1/2mv2
v2 = 2zV/m 1
When ions are shot into the magnetic field of the analyzer, they are drawn into circular motion by
the field, and at equilibrium the centrifugal force of the ion (mv2/r) is equated by the centripetal
force exerted on it by the magnet (zBv).
mv2/r = zBv
v = zBr/m 2
Combining equation 1 and 2
2zV/m = [zBr/m]2
m/z = B2r2/2V
Where; B is strength of the focusing magnet
V is accelerating voltage.

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Types of Mass Analyzer
 The Magnetic Sector Mass
Analyzer
 Double Focusing Mass
Analyzer
 Quadrupole Mass Analyzer
 Time-of-Flight Mass Analyzer
 Fourier Transform-Ion
Cyclotron Resonance
Deflection:
Ions are deflected by a magnetic field
due to difference in their masses. The
lighter mass, more they are deflected.
It also depends upon the charge on
the ion the more positive charge,
more it will be deflected.

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D. Detector, Amplifier and Recorder
The focused ion beam passes through the collector slit to the detector, which must
convert the impact of a stream of positively charged ions into an electrical current. This
must be amplified and recorded , either graphically or digitally.
Several different amplification systems are used by different manufacturers, but the
most common is the electron multiplier, which operates in a manner similar to the
photomultiplier detector. A series of up to twenty copper-beryllium dynodes transduces
the initial ion current, and the electrons emitted by the first dynode are focused
magnetically from one dynode to the next; the final cascade current is thus amplified
more than one million times.
Two essential features of the recording system in a mass spectrometer are that it must
(a) have a very fast response, and be able to scan several hundred peaks per second,
and (b) be able to record peak intensities varying by a factor of more than 103 .

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E. Data System
The analog signal coming from the detector is first converted to digital form in an
analog-to-digital convertor, or ADC, and the digitized data are stored in computer
memory. Computer-controlled instruments produce the mass spectral data in several
forms, either as a list of fragment ions or plotted directly as a bar diagram.
Improvements in instrumentation have largely eliminated the need for sets of mirror
galvanometers.
Accurate mass calibration is carried out each day by recording the mass spectrum of
appropriate reference compounds such as perfluorokerosene (PFK) or cesium iodide
clusters for very high molecular masses. Identification of known compounds can be
carried out by searching through computer-held digitized mass spectra; many
collections are available commercially containing up to 100 000 compounds on file.
Example: Mass Spectra of 1-pentanol

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5. Conclusion
Organic chemists use mass spectrometry in three principal ways:
(1) To measure relative molecular masses (molecular weights) with very
high accuracy.
(2) To detect the places at which it prefers to fragment; from this can be
deduced the presence of recognizable groupings within the molecule.
(3) As a method for identifying analytes by comparison of their mass
spectra with libraries of digitized mass spectra of known
compounds.

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6. References
 Introduction to Spectroscopy- Pavia, Lampman, Kriz, Vyvyan- Fourth
Edition (Page. No; 418-432)
 Organic Spectroscopy- William Kemp- Third Edition(Page. No; 285-292)
 A Text Book of Mass Spectrometry- Jurgen H. Gross (Page. No; 1-4)
 Principles and Applications of Mass Spectrometry-
Edmond de Hoffmann, Vincent Stroobant- Third Edition-(Page. No; 1-5)
 https://en.m.wikipedia.org/wiki/Sample_preparation_in_mass_spectromet
ry
 Mass Spectrometry animation, instrumentation and working:
 https://www.youtube.com/watch?v=PLElbY8S8u_DKLj5f46jYuC

15. Thank You