This document provides an overview of mass spectrometry. It defines mass spectrometry as a technique for determining the molecular mass and composition of organic and inorganic compounds. The document outlines the basic components and working principle of a mass spectrometer. It discusses sample ionization, mass analysis, and ion detection. Fragmentation patterns are described along with examples of mass spectra for different compound classes like alkanes, alkenes, alkynes, aromatics, and alcohols. The history of mass spectrometry is also summarized.

1. LOGO
PRESENTED BY
SALMAN ZAFAR
163
INORGANIC CHEMISTRY
S E COLLEGE BWP
PAKISTAN
salmanzafar27@yahoo.com

2. CONTENT
 DEFINATION
 INTRODUCTION
 HISTORY
 MASS SPECTROMETER
 PRINCIPLE
 STRUCTURE ANALYSIS
 FRAGMENTATION
 EXSAMPLES

3. DEFINATION
 Mass spectrometry is the most accurate
technique to determine the molecular mass
and molecular composition of organic and
inorganic compounds. It provides both
qualitative and quantitative information
about the molecular composition of organic
and in organic compounds. It is also called
positive ion spectra or line spectra.

4. •Powerful analytical technique
•Smallest scale
•Destructive technique
•Useful for identification of
species
According to the IUPAC
(International Union of Pure and
Applied Chemistry), it is the
branch of science dealing with
all aspects of mass
spectrometers and results
obtained with these instruments.

5. INTRODUCTION
 Why we say mass spectrometry not
mas spectroscopy?
 In mass spectrometry there is no
absorption of electromagnetic
radiations. It is just a measurement of
molecular weights of different
molecules in a compound according
to their m/z ratio.

6. 1897
1919
1934
1966
J.J. Thomson. Discovered electrons by cathode
rays experiment. Nobel prize in 1906.
Francis Aston recognized 1st mass spectrometer
and measure z/m of ionic compounds.
First double focusing magnetic analyzer was
invented by Johnson and Neil.
Munson and Field described chemical
ionization.
Brief History of Mass Spectrometry

7. 1968
1975
1985
1989
Electrospray Ionization was invented by Dole,
Mack and friends.
Atmospheric Pressure Chemical Ionization
(APCI) was developed by Carroll and others.
F. Hillenkamp, M.Karas and co-workers describe
and coin the term matrix assisted laser
desorption ionization (MALDI).
w. Paul discovered the ion trap technique.

8. Joseph John
Thomson
1906 Nobel Prize for
Physics
(theoretical and
experimental
investigations on the
conduction of
electricity by gases)
Francis William
Aston
1922 Nobel Prize for
Chemistry
(mass spectrograph,
of isotopes, in a
large number of non-
radioactive
elements)
Wolfgang Paul
1989 Nobel Prize for
Physics
(for the development
of the ion trap
technique)
John Bennet
Fenn
2002 Nobel Prize
for Chemistry
(for the
development of
Soft Desorption
ionization Method)
Koichi Tanaka
2002 Nobel Prize
for Chemistry
(mass
spectrometric
analyses of
biological
macromolecules)
Nobel prize pioneers

9. Mass spectrometer

10. Mass spectrometer is similar to a prism.
In the prism, light is separated into
its component wavelengths which
are then detected with an optical
receptor, such as visualization.
Similarly, in a mass spectrometer
the generated ions are separated
in the mass analyzer, digitized and
detected by an ion detector.

11. Basic Components of Mass Spectrometer
Four basic components
• Sample inlet
• Ionization source
• Mass analyzer
• Ion detector

12. Understanding Mass Spectrometry
In a mass spectrometer, the same thing is
happening, except it's atoms and
molecules that are being deflected, and it's
electric or magnetic fields causing the
deflection. It's also happening in a cabinet
that can be as small as a microwave or as
large as a chest freezer.

13. PRINCIPLE
 First of all sample is bombarded with high
electron beam produce the positive ions.
 They travel in a straight path.
 When a magnetic field or electric field is
applied they travel in curved path.
 The fragments of different masses are
separated based on the radius of curvature.
 m/z α r²
 These are then detected on detector.

14. VIDEO

15. VIDEO

16. STRUCTURE ANALYSIS
Structural analysis and
Fragmentation Patterns
Mass spectrum
Graph of ion intensity (relative
abundance) along x-axis versus
mass-to-charge ratio (m/z) (units
daltons, Da) along Y-axis
•Molecular ion (Parent ion)
•Fragmentation peaks
•Base peak
•Isotopic peaks

17. MOLECULAR ION PEAK
the peak
corresponding to the
mol. wt.of the
compound
The peak of an ion
formed from the original
molecule by electron
ionization, by the loss of
an electron, or by
addition or removal of
an anion or cation and
also known as parent
peak, radical peak.
Molecular ion (Parent ion)

18. ISOTOPIC PEAKS

19. NATURAL ABUNDANCE

20. NATURAL ABUNDANCE
M M+1 M+2
Silicon :28Si: 100 29Si: 5. 2 30Si : 3.35

21. ISOTOPIC PEAKS
79Br

22. BASE PEAK
Base peak
The most intense (tallest) peak in a mass
spectrum, due to the most abundant ion. Not to
be confused with molecular ion: base peaks
are not always molecular ion and molecular ion
are not always base peaks.

23. FRAGMENTATION
 The process of breaking molecules/ions
into fragments is known as fragmentation.
 This can be seen in the form of peaks in
mas spectra. Methanol can be divided into
four fragments. e.g.
 CH3OH → CH3OH* + e¯
 CH3OH → CH3* + OH¯
 CH30H → CH2OH* + H¯
 CH30H → CHO* + H2¯

24. FRAGMENTATION PEAKS
120
100
80
60
40
20
0
.
5 10 15 20 25 30 35
120
100
80
60
40
20
0
CHO⁺
CH3OH⁺
CH3⁺
CH2OH⁺
m/e

25. RULES OF
FRAGMENTATION
 Intensity of M+ is larger for linear chain
than for branched compounds.
 Intensity of M+ decrease with increasing
molecular weight. (exception of fatty acids)
 Cleavage is favored at branching.
 Aromatic rings, Double bond, Cyclic
structure stabilize M+

26. RULES OF
FRAGMENTATION
1.Hydrocarbons
•Hydrocarbons give clusters of peaks.
•Molecular ion peaks of very low abundance are observed for linear
hydrocarbons.
•For branched hydrocarbons give a low intensity at M+.
•Intensity of (CnH2n+1) peaks decreases with increasing mass.

27. STRUCTURE ANALYSIS
•DBR Calculations
•Nitrogen Rule

28. STRUCTURE ANALYSIS
DBR Calculations
Double bond or ring calculations tell us
about how many rings or double bonds are
present in a compound.
DBR= C-H/2+N/2+1
C= number of carbon atoms
H= number of hydrogen atoms
N= number of nitrogen atoms

29. STRUCTURE ANALYSIS
Nitrogen Rule
If a compound contains an even
number of nitrogen atoms (or no
nitrogen atoms), its molecular ion
will appear at an even mass
number.
• If, however, a compound
contains an odd number of
nitrogen atoms, then its
molecular ion will appear at an
odd mass value.
• This rule is very useful for
determining the nitrogen content
of an unknown compound.

30. Mass spectra (examples)
Alkanes
Strong M+ (but intensity decreases with an increase of branches.
Carbon-carbon bond cleavage
loss of CH units in series: M-14, M-28, M-42 etc

31. Alkanes

32. Alkenes Strong M+
Fragmentation ion has formula CnH2n+ and CnH2n-1
-Cleavage
A series of peaks: M-15, M-29, M-43, M-57 etc

33. Alkynes
Strong M+
Strong base peak at M-1 peak due to the loss of terminal hydrogen
Alpha cleavage

34. Aromatic Hydrocarbons
Strong M+
Loss of hydrogen gives base peak
McLafferty rearrangement
Formation of benzyl cation or tropylium ion

35. EXAMPLE
Alcohols
M+ weak or absent
Loss of alkyl group via a-cleavage
Dehydration (loss of water) gives peak at
M-18

36. LOGO
salmanzafar27@yahoo.com
S E COLLEG BWP
PAKISTAN