mass spectrosopy to measure the mass of unknown analyte in sample

1. MASS SPECTROSCOPY
Presented to:
Dr. Muhammad Irfan
Presented by:
Aqsa Ayoub
FORMAN CHRISTIAN COLLEGE
A CHARTERED UNIVERSITY

2. MASS SPECTROSCOPY
• A mass spectrometer is an instrument which produces
charged particles (ions) from chemical substances under
analysis.
• It then uses magnetic and/or electric fields to
separate those ions and to measure their mass.

3. MASS SPECTROMETER
Ion
Source
Mass
Analyzer
Ion
Detector
Inlet Data
System
Vacuum
Pumps
Sample
Introduction
Data
Output
It's important that the ions produced in the
ionization chamber have a free run through
the machine without hitting air molecules

4. Ion Generation
~70 Volts
+
_
+
_
e- e-e-
++ +++
+
_
Electron Collector (Trap)
Repeller
Extraction
Plate
Filament
To Analyzer
Inlet
Electrons
Neutral
Molecules Positive Ions

5. 1. Electron Ionization (EI)
vaporized sample is bombarded with high energy
electrons (typically 70 eV)
2. Chemical Ionization (CI)
Vaporized sample reacts with pre-ionized reagent gas
via proton transfer, charge exchange, electron capture,
etc.
3. Fast Atom/Ion Bombardment (FAB)
Laser Desorption & Matrix-Assisted Laser Desorption
(MALDI): hit the sample with a laser beam
4. Electrospray Ionization (ESI)
a stream of solution passes through a strong electric
field (106 V/m)
Ionization Methods

6. Atom or molecule is hit by high-energy electron
Principles of Electron-Impact Mass Spectrometry
e–

7. Atom or molecule is hit by high-energy electron
electron is deflected but transfers much of its energy to
the molecule
e–

8. This energy-rich species ejects an electron.

9. This energy-rich species ejects an electron.
forming a positively charged, odd-electron species called
the molecular ion
e–+
•

10. Atom or molecule is hit by high-energy electron from
an electron beam at 10ev
e–
beam
forming a positively charged, odd-electron species
called the molecular ion
e–
+
•

11. Acceleration
The positive ions are repelled away from the very positive
ionization chamber and pass through three slits, the final
one of which is at 0 volts. The middle slit carries some
intermediate voltage. All the ions are accelerated into a
finely focused beam

12. Magnetic Mass Separation
• The magnetic field exerts a force on these fast-moving
ions and causes them to move in a circular path, the
radius of which is dependent upon their mass to charge
ratio (m/z) and speed.
ion not detected
m/z too large
ion not detected
m/z too small
Correct m/z ratio
ion detected
Ion
Source
Detector
S
N
Electromagnet

13. Molecular ion passes between poles of a
magnet and is deflected by magnetic field
amount of
deflection depends
on mass-to-charge
ratio
highest m/z
deflected least
lowest m/z
deflected most
+
•

14.  If the only ion that is present is the molecular
ion, mass spectrometry provides a way to measure
the molecular weight of a compound and is often
used for this purpose.
 However, the molecular ion often fragments to
a mixture of species of lower m/z.(fragmentation)

15. +
•
The molecular ion dissociates to a cation
and a radical.

16. The molecular ion dissociates to a cation
and a radical.
+ •
Usually several fragmentation pathways are
available and a mixture of ions is produced.

17. • mixture of ions of
different mass
gives separate peak
for each m/z
• intensity of peak
proportional to
percentage of each
ion of different
mass in mixture
• separation of peaks
depends on relative
mass
+
+
+
+
+
+

18. + + + +
+ +
• mixture of ions of
different mass
gives separate peak
for each m/z
• intensity of peak
proportional to
percentage of each
ion of different
mass in mixture
• separation of peaks
depends on relative
mass

19. Detection and recording of
sample ions.
• The detector monitors the ion current, amplifies it and the
signal is then transmitted to the data system where it is
recorded in the form of mass spectra .
• The m/z values of the ions are plotted against their
intensities to show the number of components in the
sample, the molecular mass of each component, and the
relative abundance of the various components in the
sample.
• The type of detector is supplied to suit the type of analyser;
• photomultiplier
• electron multiplier
• micro-channel plate

21. Summary

22. Pharmaceutical analysis
Bioavailability studies
Drug metabolism studies, pharmacokinetics
Characterization of potential drugs
Drug degradation product analysis
Screening of drug candidates
Identifying drug targets
Biomolecule characterization
Proteins and peptides
Oligonucleotides
Environmental analysis
Pesticides on foods
Soil and groundwater contamination
Forensic analysis/clinical
Applications of Mass Spectrometry