|| MASS SPECTROMETRY
Sri Krupa Institute of Pharmaceutical Sciences
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= Mass spectrometry is one of the most
generally applicable tools providing both
qualitative and quantitative information
about the atomic and molecular materials.
= Here the compound under the investigation is
bombarded with a beam of electrons which
produce an ionic molecule or ionic fragments
of the original species. The resulting charging
particle is then seperated according their
= Analytical method to measure the
molecular or atomic weight of samples
ma Geed =
=” Organic molecules are bombarded with
electron and are converted to high energetic
positively charged ions(molecular ions or
# Which will break up in to smaller ions
(fragment ions or daughter ions).
= The loss of electron from a molecule leads to
a radical cation.
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This molecular commonly M* decomposes to a pair
of fragments which may be either radical +anion or
a small molecule + radical cation.
These molecular ions, are isolated in the electric
field at an voltage V, these charging particles which
are isolated then made to enter into an magnetic
field H. Here the field attracts the particles and
move ina circle around it.
Here the radius of the ionised molecule depends on
m, its mass. This forms the basis of separation of
particles according to their masses.
These ions are made to impinge upon the collector
inturn thus giving rise to a spectrum.
The ion source, ion path and collector of the mass
spectrometer must be under high vacuum(107 mm
Hg) for optimum operation.
SAMPLE INLET SYSTEM
ION SOURCE(OR IONISATION CHAMBER)
THE ELECTROSTATIC ACCELERATING SYSTEM
THE MAGNETIC FIELD
THE ION SEPERATOR
THE ION COLLECTOR
THE VACUUM SYSTEM
SAMPLE INLET SYSTEM
1. Handling gas samples:
It involves transfer of samples from small containers of
known volume coupled to a mercury manometer. The
sample is then expanded into a reservoir immediately a
head of the sample inlet
2.Introduction of liquids:
The sample is converted into gaseous state then injected
by using a
a. micropipet to a sintered glass disk under a layer of
b. by hypodermic needle injection through a silicone
3. Handling of solids:
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pressure can be
introduced directly into
an entrance to the ion
chamber ona silicon
= Volatilised by gently
heating until sufficient
vapour pressure Is
indicated by the total
ion currrent indicator.
Gas Ionization techniques
Means of ionization
Fast atom bombardment(FAB) Impact of high velocity atoms onasample
dissolved ina liquid matrix.
Secondary ion MS(SIMS) Impact of high beatae ona thin film of sample on
a metal substrate (or dissolved in a liquid matrix.
Impact of nuclear fission fragments., e.g. Using
Plasma desorption isotope on solid sample deposited on a metal foil.
Matrix Assisted Laser Desorption /lonization
Field Desorption Impact of high energy photon on asample
embedded ina solid organic matrix
Imposition of high electric field gradient on
sample deposited on a special solid support
The positive ions formed in the ionisation chamber are
withdrawn by the electric field which exists between the
first accelerator plate and the second repeller plate.
= Astrong electrostatic field between accelerator and
repeller plate of 400-4000 accelerates the ions of masses
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= The ions which escape through slit having velocities and
kinetic energies give
= when ever the mass spectrometer is started to record the
spectrum, the second accelerator is charged to ana
potential of 400V
= As the accelerated particles from the
electrical field enter magnetic field, the force
of magnetic field requires to move in a curved
= The radius of this curvature, r, is dependent
upon the mass m, the accelerating voltage, V,
the electron charge, e, and the strength of
the magnetic field, H.
= Itis the two properties m/e and r upon which
mass spectroscopy is based.
| BAS Sammpie ions accelerate magnetic held
enters here towards charged deflects lightest ions
od J Lyds
lonives the gas
ions separated by mass
Ion seperators or analysers
Double focussing analyser
Cycloidal focussing analyser
Quadrupole mass spectrometer
Time of flight
Radio frequency analysers
Quadrupole Mass Analyser
=” Quadrupole Mass spectrometer, initially
devised to separate uranium isotopes.
= Focusing of ions after accelerating from the
ion source is affected by a quadrupole mass
filter where they are separated according to
mass and detected by an electron multiplier.
= The mass filter consists of a quadrant of four
parallel circular tungsten rods which foce ions
by means of an oscillating and variable
= The ion beam currents are of the order of
10*> to 10°9 ampere.
= The generally employed ion collectors are
photographic plates, Faraday cylinders,
electron multipliers and electrometers.
= Ahigh vacuum is to be maintained.
= The inlet system is generally maintained at
0.015 torr, the ion source at 1075 torr and
analyzer tube at 107 torr or as low as
= Ojl diffusion and mercury diffusion pumps are
commonly used in different types of
= Structure elucidation
= Detection of impurities
= Quantitative analysis
= Drug metabolism studies
” Clinical, toxicological and forensic
1. Instrumental methods of chemical analysis by
Gurdeep R. Chatwal, Sham k. Anand, first
edition page no 2.273-2.285
Organic spectroscopy by William Kemp, Third
edition page no 285-290.
Spectrometric identification of organic
compounds by Silverstein. Sixth edition page no
Instrumental methods of analysis by Willard,
seventh edition page no -466
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