This document discusses several ionization techniques used in mass spectrometry including electron impact ionization, chemical ionization, field ionization, MALDI, FAB, ESI, APCI, APPI, and their applications. It also describes the working of common mass analyzers like quadrupole mass analyzer and time-of-flight analyzer. Finally, it mentions some applications of mass spectrometry like protein characterization, isotope tracking, molecular weight determination, studying reaction mechanisms etc.

2.  Electron Impact Ionization
 Chemical Ionization
 Field Ionization
 MALDI
 FAB
 ESI
 APCI
 APPI
 QMA
 TOP
 APPLICATION

3. PRESENTED BY
SUMEL ASHIQUE (M.PHARM,PHARMACEUTICS)
Sem-1st ,session – (2018-2019)

4.  A beam of electrons passes through a gaseous phase sample & collides
with neutral analyte moleculeas to produce a positively charged ion or
fragment ions.
 Generally electrons with 70 ev are used to
form fragment ion.
 The positive ions are collected in focusing
Plates & passed to mass analyzer.

5.  Process is initiated with a reagent gas such as Methane,NH3 which is
ionised by electron impact.
 High gas pressure in the ionization
Source is required for the reaction
between the reagent gas ions & reagent
gas neutrals .
 O2 & H2 are used in negative
Ionisation.

6.  Molecules pass through sharp metal anode that carrying an electric
field which produce ions from gas-phase.
 Excellent for high molecular and non-polar compounds.
 Electrons are analysed in primary focussing cathode slit.

7.  Immobilized matrix is bombarded with a fast beam of argon or
xenon.Charged sample ions are ejected from the matrix & extracted
into the mass analyzer.
 Used for large compounds with low volatility( such as protein
,peptides).
 Solid or liquid sample is mixed with a non-volatile matrix (
glycerol,crown ether)

8. This technique uses a laser energy absorbing matrix to create ions
from large molecules with minimal fragmentation.
MALDI involes 3 step process:
First, the sample is mixed with a suitable matrix material and applied
to a metal plate.
Second, a pulsed laser irradiates the sample, triggering ablation and
desorption of the sample and matrix material.
Finally, the analyte molecules are ionized by being protonated or
deprotonated in the hot plume of ablated gases, and then they can be
accelerated into whichever mass spectrometer is used to analyse
them.

10.  Here corona discharge is used to ionize the analyte in the
atmospheric pressure region.
 The liquid effluent of APCI is introduced directly into the ionisation
source which contains a heated vaporizer that facilitates rapid
desolvation of droplets.
 which utilizes gas-phase
ion-molecule reactions at
atmospheric pressure (10ˆ5 Pa).

11. The sample solution is sprayed from a region of the strong electric
field at the tip of a metal nozzle.
Either dry gas,heat,or both are applied to the droplets at atmospheric
pressure thus causing the solvent to evaporate from each droplet.
NANO ESI:
The spray needle has been made very small & positioned close to the
entrance of mass analyser.
 Advantages: Increased efficiency
Reduction in the amount of sample needed.

13. First the sample (analyte) is mixed with a solvent. Depending on the
type used, the solvent could increase the number of ions that are
formed.
The liquid solution is then vaporized with the help of a nebulizing gas
such as nitrogen, then enters an ionization chamber at atmospheric
pressure. There, the mixture of solvent and sample molecules is
exposed to ultraviolet light from a krypton lamp. The photons
emitted from this lamp have a specific energy level (10 electron volts,
or eV)

14. that is just right for this process: high enough to ionize the target
molecules, but not high enough to ionize air and other unwanted
molecules. So only the analyte molecules proceed to the mass
spectrometer to be measured.
Reaction : M + hν ⇨ M+• + e-

15. An ion after leaving ion source the ions are separated according to
their m/e ratio.
In this area the ions are accelerated by both electrostatic &
magnetically.
Types:
1. Quadrupole Mass analyzer ( QMA)
2. Time of Flight Analyzer (TOF)
3. IonTrap Analyzer
4. Double Focusing Analyzer
5. Ion cyclotron Analyzer

16.  The quadrupole consist of 2 pairs of parallel metal rods with
applied DC & Radio frequency voltage by which the ions are
scanned.
 Ions travel parallel to 4 rods & try to follow alternating field in
helically.

17.  Time-of-flight mass spectrometry (TOFMS) is a method of mass
spectrometry in which an ion's mass-to-charge ratio is determined
via a time of flight measurement.
 Ions are accelerated by an electric field of known strength. This
acceleration results in an ion having the same kinetic energy as
any other ion that has the same charge.
 The velocity of the ion depends on the mass-to-charge ratio
(heavier ions of the same charge reach lower speeds, although
ions with higher charge will also increase in velocity).

18.  The time that it subsequently takes for the ion to reach a detector
at a known distance is measured. This time will depend on the
velocity of the ion, and therefore is a measure of its mass-to-
charge ratio.

19.  Protein characterization: ESI & MALDI are used to determine the
function and stricture .
 Isotope tracking: Used to determine the isotopic composition of
elements within a sample
 Molecular weight: By using relative intensities ( peak height),we
can calculated the actual numbers of C,H,O atom.
 Bonding: Can be studied by fragmentation patterns for example-
beta cleavage is possible by only if double bonds or heteroatom is
present.
 Reaction mechanism: In carboxylic acid and alcohols a peak at M-
18 ,indicates water is present.

20.  Sharma Y.R.Elementary organic spectroscopy principles and
chemicalk application.1st ed. S.Chand and Company ltd; New
Delhi: 2008
 Skoog DA,West DM.Principle of instrumental Analysis.2nd
edition