Mass spectrometry is a technique used widely in science to determine the relative atomic mass of elements, molecular mass of compounds, and structure of compounds. It works by ionizing sample vapors with an electron beam, which causes fragmentation of molecular ions. A mass analyzer then separates the ions by their mass-to-charge ratio to produce a mass spectrum. Common ionization techniques include electron ionization, chemical ionization, field desorption, and fast atom bombardment. Mass spectrometry has applications like molecular mass determination, isotope detection, and distinguishing between cis and trans isomers.

1. Shri Shivaji Education Society Amravati’s
J.D.Patil Sangludkar Mahavidyalaya,
Daryapur.
Mass Spectrometry
Rahul G.Sawarkar
M.Sc. GATE, SET.
Assistant Professor

2. Content
Introduction
Principle
Instrumentation
Process Of Sample Introduction
Direct Vapour Inlet
Gas Chromatography
Direct Insertion Probe
Ionisation Techniques
Electron Ionisation (EI)
Chemical Ionisation (CI)
Field Desorption (FD)
Fast atom Bombardment (FAB)
Applications
Refrences

3. Mass spectrometry is used widely in
science. It is used to determine the relative
atomic mass of elements, the molecular
mass of chemical compounds and the
structure of these compounds
Introduction

4. Sample compound converted to vapours
Energetic e- beam (70eV) bombarded on the vapours.
Ionization of the sample –
M + e- M+ + 2 e-
Fragmentation of molecular ions.
Mass analyzer ( seperation of ions)
m/e values and the mass spectrum.
Principle

5. ½ mv2 = eV
mv2/r = Hev
Finally, on solving we get –
m/e = H2r2/2V

6. Instrumentation

7. Process of Sample Introduction
Direct Vapor Inlet
Gas Chromatography
Direct Insertion Prob

8. Produces M+. radical cation giving molecular weight
◗ Produces abundant fragment ions
◗ Energetic process. A heated filament emits
electrons which are accelerated by a potential
difference of usually 70eV into the sample chamber.
Ionisation of the sample occurs by removal of an
electron from the molecule thus generating a
positively charged ion with one unpaired electron.
M + e M+. + 2e-
Ionisation Technique
1) Electron Ionisation

9. 2) Chemical Ionisation
Development from EI
Same compound classes as EI
Gives molecular weight
Softer ionisation technique
Produces M+H+ ions or M - H- ions
Used to produce more abundant molecular ions
when the molecule under investigation
fragments using EI

10. Primary ion
CH4 + e CH4+. + 2e-
CH4+ CH3+ +H.
Secondary ions
CH4+ + CH4 CH5+ + CH3
CH3+ + CH4 C2H5+ +H2
Proton donation
CH5+ + M CH4 + MH+

11. 3)Field Desorption
• The sample is deposited onto the emitter and the
emitter is biased to a high potential (several
kilovolts) and a current is passed through the
emitter to heat up the filament. Mass spectra are
acquired as the emitter current is gradually
increased and the sample is evaporated from the
emitter into the gas phase.

12. 4) Fast Atom Bombadment
Used for large compounds with low volatility (eg
peptides, proteins, carbohydrates)
◗ Solid or liquid sample is mixed with a non-volatile
matrix (eg glycerol, crown ethers, nitrobenzyl
alcohol)
◗ Immobilised matrix is bombarded with a fast
beam
of Argon or Xenon atoms. Charged sample ions are
ejected from the matrix and extracted into the mass
analysers
◗ Gives M+H+ or M+Na+ ions
◗ Choosing correct matrix is difficult

13. It has wide applications.Some of important ones
are mentioned below-
1.Molecular mass determination,
2.Isotope detection,
3.Distinguish between cis & trans-
isomers,
Applications

16. 2. Isotope Detection
Mass spectrometry is also used to determine the isotopic
composition of elements within a sample. For this highly
sensitive instrument called isotopic ratio mass
spectrometer (IR-MS) is employed.Isotopic analysis is also
useful in protein quantification.

17. 3.Distinction Between cis & trans- isomers
This technique can successfully distinguish
between the cis and trans isomers of a
compound. Both the ions give mass spectra
but the spectra of trans isomers is more
intense. Also the dehydration fragment of the
cis isomer is stronger than that of trans
isomers and thus they can be identified
separately.
Ex: 2-Butene

18. Conclusion:-
Mass spectrometry is a very
powerful analytical technique
which is being rapidly
employed for the structural
determination of large no. of
compounds.

19. Refrences
1) Introduction to SPECTROSCOPY
(third edition)
By-Donald L. Pavia
Gary M. Lampaman
George S.Kriz
2) Organic Spectroscopy
(third edition)
By- William Kemp
3)Organic Spectroscopy Principles and Application
(second edition)
By-Jag Mohan
4) Instrumental Methods Of Chemical Analysis.
By- Gurudeep R.Chatwal
Sham K.Anand

20. Thank You.....