Gas chromatograohy

Department of Pharmacy
Pokhara University
School of Health and Allied Sciences
Sandeep Karki
Bachelor in Pharmacy
Tribhuvan University , Institute of Medicine
Sunsari Technical College , Laxmi Sadak ,Dharan-4, Koshi , Nepal

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• History
• Introduction
• Instrumental Components
1. Carrier gas
2. Sample Injection Port
3. Column
4. Column Temperature
5. Detectors
• Process
• Applications
• Advantages and Disadvantages
• Conclusion
• References
Presentation on Gas Chromatography 2

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• 1903-Russian scientist Mikhail Semenovich Tswett termed the name
Chromatography
• 1941- Archer John Porter Martin developed liquid–liquid
chromatography
• 1944-Again ;Archer John Porter Martin developed paper
chromatography and laid the foundation for the development of gas
chromatography
• 1947 -German graduate student Fritz Prior developed solid state gas
chromatography
• 1950-Finally;Archer John Porter Martin produced liquid-gas
chromatography

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It is a technique for separation of mixtures into components by a
process which depends on the redistribution of the components
between a stationary phase and mobile gas.
In gas chromatography, the mobile phase is a carrier gas (usually an
inert gas ) and the stationary phase is a microscopic layer of liquid. So ,
it is also known as gas liquid partition chromatography(GLPC).Gas
chromatography is the combination of gas spectrometry and mass
spectrometry.
Purpose of these technique is to separate the chemical element of
certain compound and identify the molecular level component
In these technique , the mixture is heated to separate the element.
Once it vaporizes , it passes the column through an inert gas(most
likely to be helium) and proceeds to mass spectrometry process and it
will be than separated and its components will be identified the mass
of the analyte molecule.

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1. Carrier gas
Carrier gases for chromatographs must be of high purity and chemically
inert such as helium,argon,nitrogen,hydrogen and carbon dioxide. The
carrier gas system can contain a molecular sieve to remove water or other
impurities.
2. Sample Injection Port
The injection can be used in one of two modes : split or splitless. The
injection contains a heated chamber containing a glass liner into which
the sample is injected through the septum.The carrier gas enters the
chamber and can leave by three routes(in split mode).The sample
vapourises to form a mixture of carrier gas,vapourised solvent and
vapourised solutes. A proportion of these mixture passes onto column.

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Contd….
3. Columns
There are generally two types of column- packed and capillary.Packed
columns contain a finely divided,inert,solid support material coated
with liquid stationary phase . Most packed columns are 1.5-10m in
length and internal diameter of 2-4mm.Glass capillary column has
much thinner walls and are given strength by the polyimide coating .
They are flexible and can be wound into coils.
4. Column Temperature
For precise work, column temperature must be controlled to within
tenths of a degree . The optimum column temperature is dependant
upon the boiling point of the sample . A temperature slightly above
the average boiling point of the sample results in an elution time of 2-
30 minutes . Minimal temperature give good resolution but increase
elution times . The column temperature is increased as separation
proceeds.

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Contd….
5. Detectors
There are many detectors which can be used in gas chromatography.
Different detectors will give different types of selectivity.
• A non-selective detector responds to all compounds except a carrier.
• A selective detector responds to a range of compounds with a common
physical or chemical property.
• A specific detector respond to a single chemical compound.
• A Mass flow dependent detector usually destroy the sample and the
signal is related to the rate at which solute molecules enter the detector.
• A concentration dependent detector does not usually destroy sample and
the signal is related to the concentration of solute in the detector

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1. The carrier gas is introduced from a gas cylinder outside the machine
which contained the mobile phase .
2. The rate of flow of the carrier gas is carefully controlled to give the clear
separation of the components in the sample.
3. The carrier gas enters the machine through the sample injection port.
4. The sample is measured by using a syringe and instantly vaporizes.
5. The gases that make up the sample separate out as they move along the
column which contains the stationary phase
6. As the sample separates out and its constituent gases travel along the
column ,a detectors analysis and records them.
7. The data analyzer /recorder attached to the machine draws a
chromatogram (chart ) with peaks corresponding to the relative amounts
of the different chemicals in the sample.

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• Used to analysis , separated and identification of multi –component
volatile organic constituents in the herbal samples.
• To develop the chemical profile for the herbal pharmacopoeial standard
and to develop the analysis methods.
• To detect all the volatile compounds at the same time but very sensitive
to detect even a single compound in the sample.
• To determine the mass of volatile molecules
• To monitor the concentration level and stability of active compound in
products . Changes in composition of volatile oil may also be used as
indicators of oxidation , enzymatic changes or microbial fermentation.

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Contd….
• To analysis fatty acid and fixed oil (such as Almond oil , Soyabean oil,
Mustard oil) in the search of unsaturated fatty acids.
• Gas Chromatography with Mass Spectrometry is used to detect the
adulterer synthetic compounds.
• Gas Chromatography is used extensively in forensic science. Disciplines as
diverse as solid drug dose (pre-consumption form) identification and
quantification, arson investigation, paint chip analysis, and toxicology
cases, employ GC to identify and quantify various biological specimens
and crime-scene evidence.

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• Requires only very small amount of sample
• Equipment is easy to handle
• Results are obtained rapidly and accurately
• Useful for separating complex mixtures into components
• Very sensitive to detect the single compound in the sample
• Equipment is rather expansive

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Gas chromatography (GC ) is a common type of chromatography used in
analytical chemistry for separating and analyzing compounds that can be
vaporized without decomposition . Typical uses of GC include testing the
purity of a particular substance or separating the different components of
a mixture. The instrument used to perform gas chromatography is called a
gas chromatograph or aerograph or gas separator.
Gas chromatography is also known as vapor-phase chromatography (VPC),
or gas–liquid partition chromatography (GLPC).

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1. Dr. Rajendra Gyawali (2013),A Handbook of Pharmacognosy (1st
Edition).Nabodit Hamro Pustak Bhandar/pg.277-279
2. Pavia, Donald L., Gary M. Lampman, George S. Kritz, Randall G. Engel
(2006). Introduction to Organic Laboratory Techniques (4th Edition.) .
Thomson Brooks/ pg. 797–801.
3. http://www.explainthatstuff.com/chromatography.html

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Gas chromatograohy

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