Gas chromatography-mass spectrometry (GC MS) is an analytical method in which GC is coupled with MS to identify different substances within a test sample.

1. Gas Chromatography–
Mass Spectrometry
(GC-MS)
Presented by
Anusiya G
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2. INTRODUCTION
 Gas chromatography–mass spectrometry (GC MS) is an analytical method
in which GC is coupled with MS to identify different substances within a
test sample.
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3. PRINCIPLE
 The sample solution is injected into the GC inlet where it is vaporized and
swept onto a chromatographic column by the carrier gas (usually helium).
 The sample flows through the column and the compounds comprising the
mixture of interest are separated by virtue of their relative interaction with the
coating of the column (stationary phase) and the carrier gas (mobile
phase).
- the stationary phase is either solid (GSC) or liquid polymer (GLC).
 The latter part of the column passes through a heated transfer line and ends at
the entrance to ion source where compounds eluting from the column are
converted to ions.
 The mass spectrometer identifies and quantifies the compounds according their
mass-to-charge ratio (m/z) .
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4. Sample
 Nature :- Samples must be volatile or semi volatile thermally stable
mixtures
 State :- Organic compounds must be in solution for injection into the gas
chromatograph. The solvent must be volatile and organic (for example,
hexane or dichloromethane).
 Amount :- Depending on the ionization method, analytical sensitivities of
1 to 100 pg (0.001 to 0.1ng) per component are routine.
 Preparation :- Sample preparation can range from simply dissolving some
of the sample in a suitable solvent.
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5. INSTRUMENTATION
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Figure 1 schematic diagram of GC-MS

6. In GC
 Gas supply - Carrier gas from the cylinder is fed to the instrument through
the regulators and tubing. Generally the gases must be purified in order to
ensure the gas supply pressure and high gas purity.
 Pneumatic controls: The gas supply is regulated to the correct pressure
(or flow) and then fed to the required part of the instrument. Modern
GC instruments have Electronic Pneumatic pressure controllers –older
instruments may have manual pressure control via regulators.
 Injector - The entrance valve is connected to the chromatographic column
with the help of injector. Here the liquid samples get volatilized.
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7.  Column- Capillary GC columns are helpful in analyzing the individual
chemical compounds present in a sample. These columns are typically 10-
120 m long with of 0.10-0.50 mm internal diameter. Packed GC columns
are 1-5 meters in length with 2 or 4mm internal diameter.
 Oven -Ovens present in GC are temperature programmable, which ranges
from 50˚C to 400˚C and with cryogenic cooling can go as low as -25˚C.
 Interface: After separation in the GC system, analyte species have to be
transported to the mass spectrometer to be ionised, mass filtered and
detected. The interface in modern instruments is heated to prevent analyte
condensation.
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8. Mass spectrometer
The separation of gas phase ions is according to their mass to
charge ratio within the mass spectrometer using magnetic and/or
electric fields to differentiate ions.
 Ion source - used to create molecular ions
- the products are ionized in favor to analysis in the mass
spectrometer.
 Mass analyzer: seperates the ions produced from ion source.
 Vacuum system: GC-MS requires high levels of vacuum for
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9.  Detector: The ionic beam which emerges from the mass analyzer, must be
detected and transformed into a signal. The detector is an important part of
the mass spectrometer that records the charge induced or the current
produced when the ion hits the surface and then generates a signal.
Control Electronics
The necessary parameters of Mass Spectrometer can be selected and
controlled from this panel. MS parameters can be controlled from a
computer in modern instruments by using specially designed software
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10. ADVANTAGES
 high sensitivity -excellent detection limits. Typically low ppb to high
ppb.
 high selectivity -identification is based on two parameters not one
-(retention time and mass spectrum must match standard).
-selects analyte of interest with very high confidence
 Speed - typical analysis takes from 1/2 hour to approx. 1 hour
analysis.
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11. DISADVANTAGES
 higher capital cost.
 higher maintenance (time, expertise and money)
 for optimum results requires analyst knowledgeable in
both chromatography and mass spectrometry.
 Improper condition of GC- results in mass spectrum with
background noise
 Optimization of GC and MC based on types of
chemicals involved.
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12. APPLICATIONS
 Environmental monitoring and cleanup
 Criminal forensics
 Industrial application (analysis of inorganic gases and
aromatic solvents, etc)
 Sports antidoping analysis
 Security
 Chemical warfare agent detection
 Food, beverage and aroma analysis
 Medicine
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13. CASE STUDY
In a case study of phytochemical profiling of chloroform
of Caulerpa racemosa GC-MS analysis is done in order
to confirm the presence of phytochemicals that were
quantitatively and qualitatively analyzed. GC-MS
analysis of chloroform extract of Caulerpa racemosa
revealed 19 chemical compounds that are represented in
the GC-MS chromatogram (Figure 2) (Sivakumar et al.,
2018).
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14. CASE STUDY
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Figure 2 : GC-MS chromatogram of chloroform extract of Caulerpa
racemosa (Sivakumar et al., 2018)

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