1. GAS CHROMATOGRAPHY
– MASS SPECTROSCOPY
(GC-MS)
(Advanced Spectral Analysis)
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2. CONTENTS :
■ Introduction - Hyphenated Techniques
■ Introduction – Gas Chromatography and Mass Spectroscopy
■ Principle - Gas Chromatography-Mass Spectroscopy (GC-MS)
■ Interfaces of GC-MS
■ Ionization Techniques
■ Mass Analyzers
■ Data Handling
■ Applications
■ References
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3. HYPHENATED TECHNIQUE :
 It is define as the combination or hyphenation between Spectroscopic and separation
(chromatographic) technique is known as Hyphenated Technique.
Spectroscopic + Chromatographic Hyphenation Hyphenated Technique
 Hyphenated techniques combines chromatographic and spectral method to exploit the
advantages of both.
 Chromatography produces pure or nearly pure fractions of chemical components in a
mixture.
 Spectroscopy produces selective information for identification using standards or library
spectra.
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4. GAS CHROMATOGRAPHY :
 Gas Chromatography – “It is a process of separating components from the given crude
drug by using a gaseous mobilephase.”
 It involves a sample being vaporized and injected onto the head of the chromatographic
column. The sample is transported through the column by the flow of inert, gaseous mobile
phase. The column itself contains a liquid stationary phase which is adsorbed onto the
surface of an inert solid.
 INSTRUMENTATION PARTS OF GC :
 Carrier Gas
 Sample Injection System
 Separation Column
 Detectors
 Amplification
 Recorder
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5. MASS SPECTROSCOPY :
■ The mass spectroscopy is an technique in which, the compound under investigation is
bombarded with beam of electrons which produce an ionic molecule or ionic fragments of the
original species.
■ The mass spectrometer is an instrument in which the substance in gaseous or vapour state is
bombarded with a beam of electrons, to form a positively charged ions (cations) which are
further sorted according to their mass to charge ratio to record their masses and their
abundances.
■ INSTRUMENTAION PARTS OF MS :
 Sample Handling System
 Ionization Chamber
 Ion Separator or Mass Analyzer
 Ion Collector, Detector and Read Out System
 Vacuum System
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6.  GAS CHROMATOGRAPHY – MASS SPECTROSCOPY
(GC-MS) :
■ GC-MS, which is a hyphenated technique developed from coupling of GC and MS, was the first of its kind to
become useful for research and development process.
■ Mass spectra obtained by this hyphenated technique offer more structural information based on the
interpretation of fragmentations. The fragment ions with different relative abundances can be compared with
library spectra.
■ Compounds that are adequately volatile, small, and stable in high temperature in GC conditions can easily be
analyzed by GC-MS.
■ In GC-MS, a sample is injected into the injection port of GC device, vaporized, separated in theGC column, analyzed by
MS detector, and recorded.
■ The time elapsed between injection and elusion is called “retention time” (tR). 6

7.  NEED OF GC-MS :
 It is important type of technique is used for the separation of organic and in organic compounds and it
is having ability for separation high molecular weight hydrocarbons. It is important type of technique
is used for separation and identification of volatile compounds. It is important for determination of
fragmentation pattern of compounds. It is also important for determination of protein, peptides, amino
acid, nucleic acid, as well as naturally or biological compounds. It is one of the powerful technique is
used for qualitative and quantitative analysis.
 ADVANTAGES OF GC-MS :
 It is important for identification of compound.
 It can provides sensitive response to most analytes.
 It is important to provide information of particular or specific class of compound.
 It can provide information of structure or different structure of compound.
 It is having high resolution and separation capacity.
 It is time saving technique, having a high resolution capacity.
 It is important determination of molecular weight as well as fragmentation pattern of compound.
 Good Accuracy and Precision.
 It is simple, rapid, reproducible technique.
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8. Gas
chromatography
Mass spectrometry GC-MS
Separates
mixture of
components
intoindividual
Identifies
molecules
based ontheir
mass
A chemicalanalysis
technique
combining two
instruments to
provide for
powerfulseparation
& identification.
WORKING OF GAS CHROMATOGRAPHY - MASS SPECTROSCOPY
[GC-MS] :
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9. COUPLING OF GC TO MS:
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GC
Atmospheric
densityheated
(200-300 ∘C)
Interfaces
MS
Highvacuum
(10-6torr)
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.

10. INTERFACES OF GC-MS :
 The interfaces between the GC and MS has an important role play in overall efficiency of the
instrument.
 It must be capable of providing an inert pathway from the column to the ion source without
loss of chromatographic resolution, while at the same time removing of carrier gas and
reducing the pressure from about one atmosphere at the column outlet to 10-5 – 10-6 mmHg in
the ion source.
 It is hardly surprising that the separator has been a major cause of technical problems
encountered in GC/MS.
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TYPES OF
INTERFACES
Witson-Biemann
Effusion Separator
Ryhage Jet
Separator
Llwellyn-Littlejohn
Separator

11.  WITSON-BIEMANN EFFUSION SEPARATOR :
■ The Witson-Biemann Effusion Separator consists of a sintered glass tube, the surrounded of which
are evacuated.
■ The carrier gas, usually helium, passes preferentially through the sintered glass and the effluent is
concentrated by a factor of up to 100.
■ Two stage separator may enrich the effluent by a factor of 400 and be capable of dealing with glass
flow rates in order of 20-60 ml/min.
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12.  RYHAGE JET SEPARATOR :
 The Ryhage Jet Separator is based upon the differing rates of diffusion of different gases in an
expanding supersonic jet stream.
 The heavier (sample) compound concentrates in the center of the gas jet.
 The gases pass at high speed through an orifice aligned with a second orifice, and then on to the
ion source, while the carrier gas is pumped away.
■ Usually a Ryhage separator is two stage, although all glass single stage units are used, particularly
in combination with quadrupole mass spectrum.
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13.  LLWELLYN-LITTLEJOHN SEPARATOR :
■ in the Llwellyn-Littlejohn separator separation of organic molecules from carrier gas molecules is
achieved by means of the selective permeability of an elastomer membrane.
■ Permeability is a function the solubility of the gas molecules in the membrane and their ability to
diffuse through it.
■ Gases such as hydrogen, helium argon and nitrogen having a very low solubility and high diffusion rate,
pass through the membrane much more slowly than organic vapors where the revers is true.
■ The vapor is therefore concentrated and the remaining carrier gas expelled into the atmosphere.
■ The concentrated is further enriched by passes through a second semi-permeable membrane.
■ Enrichment of the organic phase by a factor of greater than 10-5 has been achieved.
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14. IONIZATION TECHNIQUES :
IONIZATION
TECHNIQUES
Electron Impact
Chemical
Ionization
Negative
Chemical
Ionization
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15.  ELECTRON IMPACT :
 In the Electron Impact (EI) process, electrons are emitted from a heated filament (usually
made of tungsten or rhenium) and are accelerated across the source by using an
appropriate potential (5-100V) to achieve the required electron energy (sufficient to ionize
the molecule).
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16.  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.
 A permanent magnet is positioned across the ion chamber to produce a magnetic flux in
parallel to the electron beam.
 A (+) ve ion repelled voltage & (-) ve ion excitation voltage works to gather to produce an
electric field in the source chamber.
 Such that ions leaves through ion exit slit.
 The ions are directed through the various focusing & centering lenses are focused on to the
source exit slit.
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17.  CHEMICAL IONIZATION :
■ Chemical ionization involves the ionization of a reagent gas, such as methane at relatively
high pressure (~1 mbar) in a simple electron impact source.
■ Once produced, the reagent gas ions collide with the analyte molecules producing ions
through gas phase reaction processes such as proton transfer.
■ 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.
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18.  NEGATIVE CHEMICAL IONIZATION :
 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.
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19. MASS ANALYZERS :
■ 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.
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Mass
Analyzers
Quadrupole Ion Trap
Time Of
Flight

20.  QUADRUPOL :
 A Quadrupole massfilter consists of four parallel metal rodswith different charges
 Twoopposite rods haveanapplied +potential and the othertwo rods havea- potential
 Theapplied voltages affect the trajectory of ions travelingdown the flight path
 For given D C and A C voltages, only ions of a certain mass-to-charge ratio pass through the
quadrupole filter and all other ions are thrown out of their original path.
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21.  ION TRAP :
 It usesanelectric field for the separation of the ion bymass to chargeratios.
 The electric field in the cavity due to the electrodes causes the ions of certain m/z values to orbit in the
space.
 The ion trap mass analyzer 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.
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22.  TIME OF FLIGHT (TOF) :
 TOF mass analyzer is based on simple idea that 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.
• TOF Analyzers separate ions by time without the use of an electric or magnetic field.
• In a crude sense, TOF is similar to chromatography, except there is no stationary/mobile phase,
instead the separation is based on the kinetic energy and velocity of the ions.
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23.  FOURIER TRANSFORM ION CYCLOTRON RESONANCE
(FT-ICR) :
 Usesamagnetic field in order to trap ions into an or bit inside of it.
 In this analyzer there is no separation that occurs rather all the ions of a particular range are
trapped inside, and an applied external electric field helps togenerate asignal.
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24. DATA HANDLING :
 All the mass spectrometers now employ computer control of same functions and also use
a computerized 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 and
if, GCMS analyses is being performed, a complete mass spectrum is generated and stored
every sec for upto 90 min
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25. APPLICATION :
 Analysis of Natural Products and Traditional Herbal Medicine
 Identification of Metabolite
 Bio analysis / Bioequivalence Studies
 ADME (Absorption, Distribution, Metabolism, and Excretion) Screening
 Dissolution Testing
 Method Development / Validation
 Forced Degradation Studies
 Impurity Profiling
 Manufacturing / QA / QC
 Analysis of amino acid
 Determination of pesticides
 Pharmacokinetic studies
 Biotechnology
 Clinical research
 Biochemical analysis 25

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