Central University of Rajasthan Akram khan

1. MASS SPECTROSCOPY
By
Akram Khan

2.  Mass spectroscopy is one of the primary spectroscopic methods for
molecular analysis available to organic chemist.
 It is a microanalytical technique requiring only a few nanomoles of
the sample to obtain characteristic information pertaining to the
structure and molecular weight of analyte.
 It involves the production and separation of ionised molecules and
their ionic decompositon product and finally measurement of
the relative abundance of different the ions produced. It is, thus a
destructive technique in that the sample is consumed during analysis.

3. Principle
 Mass spectroscopy is the most accurate method for determining the
molecular mass of the compound and its elemental composition.
 In this technique, molecules are bombarded with a beam of energetic
electrons.
 The molecules are ionised and broken up into many fragments, some
of which are positive ions.
 Each kind of ion has a particular ratio of mass to charge, i.e. m/e
ratio(value). For most ions, the charge is one and thus, m/e ratio is
simply the molecular mass of the ion.

5. Instrumentation

6. cc

7. solid
Directly into the
chamber with low
vapour pressure
by means of
probe.
e.g. steroids,
carbohydrates
Vaporized with
the help of heat
inlet system.
e.g. sugars ,
amino acids
Gas
Directly inleted &
vaporized
Liquid

8. Electron
impact
ionization
Chemical
ionization
Field
ionization
Laser
desorption
technique
Fast acting
bombardme
nt
8
IONIZATION TECHNIQUE

9. ELECTRON IMPACT IONIZATION

10. CHEMICAL IONIZATION
Reactive gases bombards with
electron beam
Reactive species are formed which
colloid with sample molecules
+vely charged ions are produced
1
0

11. Fast atoms
of Xe/Ar
collides
with neutral
gas atoms
Transferof
energy to
gas atoms
High
energy gas
atoms
directed
towards
sample
Energy
transfer to
sample
Fast atom bombardment

13. Laser desorption ionization

14. +
-
+
+ -
+ -
+
+ +-
Analyte
Matrix
Laser
+
+
+ + -+
- +
+
+ +
Laser is bombarded with
Matrix containing thesample
Energy transfer to sample
Expansion of matrix

15. +ve ions at the end of
chamber
Bombarded with
accelerating
potential(2-8kV)
Deflection inmagnetic
field according to
velocity & m/e
1
5
Analyzers are
used to deflect
ions based upon
m/e ratio.
MASS ANALYSER

16. SINGLE FOCUSING MAGNETIC ANALYSER

17. DOUBLE FOCUSING MAGNETIC ANALYSER

18. Magneticfield
Ions of same mass
number are
separated
Less
sensitivity(10-1)
Magnetic field &
electric field
Ions of same mass
no.& same velocity
are separated
Highly
sensitive(10-12)
18

19. QUADRAPOLE MASS
ANALYSER

20. sensitive.
1000 times
greater than
faraday cup.
Least
sensitive.
Cup will
capture the
ion.
Most
sensitive.
Used for
high
resolution.
Photomult
iplier
detector
Photogra
phic
detectors
Faraday
Cup
detector
20
DETECTORS

22. Identification of fragmentation pattern
Impurity detection
As LC-MS in analysis ofproteins
22
Identification of an unknown compound
Molecular weight , formula &elemental
composition determination
Identification of an unknown compound
APPLICATIONS

23. SPECTRA