hyphenated techniques

1. GAS CHROMATOGRAPHY-
MASS SPECTROMETRY (GC-MS)
Presented By,
Pradeep s jaiswal.
Msc.part-2.
semester-4.
paper-2.

2. CONTENTS :
•Introduction to GC-MS.
•Gas chromatography.
•Mass spectrometer.
•coupling of GS to MS.
•Types of Interfaces.
•Ionization sources and techniques.
•Mass analyzers.
•Limitation of GC-MS.
•Application of GC-MS.
•References.

3. Gas
Chromatography
It separates
components of
sample
Interface
Combines both
techniques by
removing pressure
incompatibility
problem between
GC and MS
Mass spectrometry
Ionise eluted
component and
separate, identify it
according to its
mass to charge ratio
INTRODUCTION TO GC-MS
Gas chromatography–mass spectrometry (GC-MS, or alternatively
HPLC-MS) is an ADVANCED ANALYTICAL
INSTRUMNTAL technique that combines the physical
separation capabilities of GAS CHROMATOGRAPHY with the
mass analysis capabilities of MASS SPECTROMETER.

4. GAS CHROMATOGRAPHY
• Gas chromatography leads to
Separation of volatile organic
compounds.
• Separation occurs as a result of
unique equilibrium established
between the solutes and the
stationary phase (the GC
column).
• An inert carrier gas carries the
solutes through the column.
Distribution Coefficient :
Concentration of component A in stationary phase.
Concentration of component A in mobile phase.
Different affinity of any 2 components to stationary phase causes the separation.

5. Principle of GC
In GC the main principle of separation is partition.
The chromatographic process – partitioning.
MOBILE PHASE
(gas or liquid)
Sample
in
Sample
out
STATIONARY PHASE
(solid or heavy liquid coated onto a solid or support
system)

6. Component OF GC
6
1. Carrier Gas.
2. Injector.
3. Pneumatic controls.
4. Oven.
5. Column.
6. Detectors:Flame Ionization Detectors
(FID)
• Electron Capture Detectors (ECD)
• Electron impact/chemical ionization (EI/CI)
Mass spectrometry

8. Diagram of mass spectromter

9. Molecular ion peakBase peakFragment ions
• BASE PEAK:The most intense peak in the mass spectrum is called the base
peak. Base peak is the highest peak it is assigned a relative intensity of 100%.
• MOLECULAR ION PEAK:The ion formed from a molecule by removal of
one electron of lowest ionization potential is known as molecular ion.
• FRAGMENT IONS:The ions produced from the molecular ion by cleavage
of bonds are called fragment ions.
• METASTABLE IONS:Mass spectrum of molecule shows sharp peaks at m/z
integrals. But some show diffuse, broad low intensity peaks at non integral
m/z values these are called metastable ions.
MASS SPECTRUM

10. GC-MS
•It’s a Hyphenated Technique.
•Invented By James & Martin in 1952.
Gas
chromatography
Mass spectrometry GC-MS
Separates
mixture of
components
into individual
Identifies
molecules
based on their
mass
A chemical analysis
technique
combining two
instruments to
provide for
powerful separation
& identification.

11. upling of GC to MS
GC
Atmospheric
density heated
(200-300 ∘C)
Interfaces
MS
High vacuum
(10-6 torr)
heated
The interface b/w the GC&MS is an important role to play in the overall
efficiency of the instrument.
Both system are heated (200 -300 ∘C) both deal with compounds in the
vapor state.
Only one problem is that the atmospheric pressure output of the GC must
be reduced to vacuum of
10-5 – 10-6 torr for the MS inlet.

12. Types of interfaces:
Capillary direct interface
Jet separator
(column packed)
Watson-Biemann effusion
separator
12

13. Capillary direct interface:
Today most GC-MS systems use capillary columns &
fused silica tubing permits an inert,high efficiency,direct
transfer between the 2 systems.
Flow rates is 5ml/min.

14. Jet separator (packed column)
•The separator consist of two glass tubes aligned with a
Small distance between them.
•Carrier gas entering from the GC column is pumped
away by a separate vacuumed system.
•The larger sample molecules maintain their momentum
&pass preferentially in to the second capillary.
•Sample enrichment occurs & the initial atmospheric
pressure is reduced.

15. • It consists of a sintered glass tube .
• The carrier usually Helium, passes preferentially through the
sintered glass tube & the effluent in concentrated by a factor of
up to 100.
• The gas flow rates in the order of 20-60ml/min.
Watson & Biermann effusion separato

16. It converts the components of a sample into ions by
bombardment with electrons, ions, molecules.
IONIZER;
CH3OH + 1e CH3OH+ + 2e
molecular ion or radical ion
The gas molecules exiting the GC are bombarded by a high
energy electron beam.

17. 1
• ELECTRON IMPACT
2
• CHEMICAL IONIZATION
3
• NEGATIVE CHEMICAL IONIZATION

18. • The most common form of ionization is EI.
• Electrons are produced by tungsten filament.
• These electrons accelerated towards the ion source chamber.
• The electrons require an energy equal to the voltage B/W the
filament & ion source chamber.
• A proportion of electron beam will strike the electron trap
producing trap current.

20. • In CI a reagent gas methane or ammonia or isobutene are
introduced into the mass spectrometer.
• The reagent gas will interact with the electron to produce
radical electrons.
• R + e R+ + 2e

22. Negative ion chemical ionization(NICI):
In NICI a reagent gas is used & the electrons collide with it so that their
energies are reduced to 10Ev.
Molecules with a high affinity for electrons are able to
capture these low energy thermal electrons.
This is known as NICI but it does not involved in the
formation of a chemical adduct.

23. Ionization
method
electron impact Chemical
ionization
Typical analyses Relatively small
volatile
Relatively small
volatile
Sample introduction GC (or) liquid/solid
probe
GC/Liquid /solid
probe
Mass range 1-1000 Dolton's 1-1000 Daltons
Method highlights Hard method
versatile
provides structure
information
Soft method
molecular ion peak
(M+H)+

24. Mass analyzers
Quadrupole Ion trap Time of flight
They deflects ions down a curved tubes in a magnetic fields based on
their kinetic energy determined by the mass, charge and velocity. The
magnetic field is scanned to measure different ions.

25. 25
• A set of four rods are arranged parallel to the direction.
• Here a DC current and radio frequency RF is applied to generate
oscillating electrostatic field in between the rods.
• Based on this only m/z is been determined.
Quadrupole

26. 2613/9/2014 VIGNAN PHARMACY COLLEGE
• The velocities of two ions are created by uniform electromagnetic force applied
to all the ions at same time, causing them to accelerate down a flight tube.
• Lighter ions travels faster and strike the detector first so that the m/z ratio of ions
is detected.

27. • The ion trap mass analyser operates by
similar principles where it consists of
circular ring electrode
• Plus two end caps that form a chamber. Here
AC or DC power along RF potential is
applied between the cups and the ring
electrode.
• There the ions entering into the chamber
are trapped by electromagnetic fields and
they oscillates in concentric trajectories.
This process is called resonant ejection.

28. • All the mass spectrometers now
employ computer control of same
functions and also use a
computerised display and output.
• The amount of data generated
even by a fairly modest mass
spectrometer is very large indeed,
a single run may store data for
upto 100 fragments from each
type of molecule.
DATA HANDLING

29. •Only Compounds with Vapour Pressure exceeding about 1010 torr
can be analyzed by Gas chromatography –mass spectrometry.
•Certain isomeric compounds cannot be distinguished by mass
spectrometry (EG : naphthalene vs. azulene).
limitation of GC-MS

30. • GC-MS is becoming the tool of choice for tracking organic
pollutants in the environment.

31. • GC-MS can analyze the particles from a human body in order
to help link a criminal to a crime.
• GC-MS especially useful here as samples often contain very
complex matrices &results used in court.

32.  GC-MS used for detection of illegal narcotics & may
eventually supplant drug-sniffing dogs.
 It’s also commonly used in forensic toxicology to find drugs
&poisons in biological specimens of victims .

33.  GC-Ms is main tool used in sports anti doping laboratories to
test athletes urine samples for prohibited performance
enhancing drugs.
EG : anabolic steroids.

34. • Food & beverage contain numerous aromatic compounds ,
some naturally present in the raw materials &some forming
during process.
• GC-MS is extensively used for the analysis of these
compounds which include ester, fatty acids , alcohols,
aldehydes, terpenes etc……

35.  GC-MS 2 were brought to mars by the Viking program.
 Venera11&12 pioneer Venus analyzed the atmosphere of
Venus with GC-MS.
 The material in the comet 67p will be analyzed by the
rosetla mission with a chiral GC-MS in 2014.

36. • In born errors of metabolism are now detectable by new born
screening tests, especially the testing using GC-MS .
• It can determine compounds in urine even in minor
concentration.
• The measurement of c13-c12 ratio with an isotope ratio mass
spectrometer.

37. • Fundamental of analytical chemistry, D.A skoog,5th edition.
• Instrumental method of analysis,H.H. willard 6th edition.