Gas chromatography is an analytical technique used to separate and analyze volatile compounds. It works by distributing the sample between a stationary phase and a mobile gas phase. Key components of a gas chromatography system include the carrier gas, injector, column, and detector. The column allows separation of compounds based on differences in partitioning between the stationary and mobile phases. Detectors then provide a quantitative measurement of separated components. Common applications of gas chromatography include analysis of pharmaceuticals, foods, flavors, fragrances, and petrochemicals.

1. A SEMINAR REPORT ON
GAS CHROMATOGRAPHY
BY
ILLURI SHRAVANI
1702-16-885-012
UNDER THE GUIDANCE OF
Mrs. CEEMA MATHEW
ASSOCIATE PROFESSOR
GOKARAJU RANGARAJU COLLEGE OF
PHARMACY

2. CONTENTS
INTRODUCTION
INSTRUMENTATION
COLUMN EFFICIENCY PARAMETERS
DERIVITIZATION
APPLICATIONS
CONCLUSION
REFERENCE

3. INTRODUCTION
• Gas chromatography is a term used to describe the group of analytical separation
techniques used to analyze volatile substances in the gas phase and thermally
stable.
• In gas chromatography, the components of a sample are dissolved in a solvent and
vaporized in order to separate the analytes by distributing the sample between two
phases: a stationary phase and a mobile phase.
• Gas chromatography is one of the sole forms of chromatography that does not
utilize the mobile phase for interacting with the analyte.
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4. TYPES OF GAS CHROMATOGRAPHY
• gas-solid chromatography (GSC) and
• gas-liquid chromatography (GLC).
• Gas-solid chromatography is based upon a solid stationary phase on which
retention of analytes is the consequence of physical adsorption.
PRINCIPLE: Adsorption of molecules on stationary phase.
• Gas-liquid chromatography is useful for separating ions or molecules that are
dissolved in a solvent.
PRINCIPLE: Partition of molecules between gas (mobile phase) and liquid
(stationary phase).
MOST WIDELY USED ONE IS GLC
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5. INSTRUMENTATION
Carrier gas cylinders
flow meters
Injector
Column
Detector
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6. Schematic diagram of GAS CHROMATOGRAPHY
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7. GAS CHROMATOGRAPHY INSTRUMENT
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8. GAS CHROMATOGRAPHY WORKING PRINCIPLE 6

9. CARRIER GAS
• The carrier gas plays an important role, and varies in the GC used. Carrier gas
must be dry, free of oxygen and chemically inert mobile-phase.
• Nitrogen, Argon,ss and Helium are used depending upon the desired performance
and the detector being used. Helium is most commonly used because it is safer.
• All carrier gasses are available in pressurized tanks and pressure regulators.
• A carrier gas system also contains molecular sieve property to remove the water
and other particulates.
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10. FLOW METER
• flow meters are used to control the flow rate of the gas.
Rotameter:
It is like a burette with a float held on to a spring.
The level of the float is determined by the flow rate of
carrier gas.
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11. Soap bubble meter:
• Glass tube with a inlet tube at the bottom
• Rubber bulb store soap solution.
• When the bulb is gently pressed of soap solution is converted into a
bubble by the pressure of a carrier gas and travel up
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12. INJECTOR
• A sample port is necessary for introducing the sample at the head of the column.
• Modern injection techniques often employ the use of heated sample ports through
which the sample can be injected and vaporized.
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13. TYPES OF INJECTORS
•Split injector
•Split-less injector
•On-column injector
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14. Types of injectors cont.…
Split Injection:
• The injection is split (1:10, 1:100) with only a portion of the sample (usually 1% -
20%) actually making it to the column
Split-less Injection:
• Sample is vaporized in the injector itself and ALL of the sample is swept onto the
column by the carrier gas.
On-Column Injection:
• used widely in packed-column GC, less in capillary GC
• sample is deposited directly on the column
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16. COLUMNS
• In gas chromatography, the column is the heart of the system where the separation
of sample components takes place.
• They are classified in terms of tubing dimensions and type of packing material.
• Packed columns are generally 1.5 – 10m in length and 2 – 4mm diameter.
• On the other hand capillary columns are 0.1 – 0.5 mm id and can be 10 – 100m
long.
TYPES OF COLUMNS:
• Open tubular column
• Packed column
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17. OPEN TUBULAR COLUMN
Wall Coated Open Tubular (WCOT)
• Internal wall of capillary is coated with a very fine film of liquid stationary phase.
Surface Coated Open Tubular (SCOT)
• Capillary tube wall is lined with a thin layer of solid support on to which liquid
phase is adsorbed.
• The separation efficiency of SCOT columns is more than WCOT columns because
of increased surface area of the stationary phase coating.
Porous Layer Open Tubular (PLOT)
• Walls of capillary fused silica tubes are strengthened by a polyimide coating.
These are flexible and can be wound into coils.
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19. PACKED COLUMNS
• Packed columns are made of a glass or a metal tubing which is densely packed
with a solid support like diatomaceous earth.
• Due to the difficulty of packing the tubing uniformly, these types of columns have
a larger diameter than open tubular columns and have a limit derange of length.
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20. DETECTOR
• The detector is the device located at the end of the column which provides a
quantitative measurement of the components of the mixture.
• Each detector has two main parts that when used together they serve as
transducers to convert the detected property changes in to an electrical signal that
is recorded as a chromatogram.
Types of detectors which are commonly used
• FID-Flame ionization detector
• TCD-Thermal conductivity detector
• ECD-Electron capture detector
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21. FLAME IONIZATION DETECTORS
• In this detector N2 is used as a carrier gas.
• Mass sensitive detector
• Response depends on conducting power of ions or electrons produced on burning
of organic compounds in the flame
• No response to inorganic and permanent gases such as CO, CO2, NH3, CS, etc.
• It is the most widely used detector in Gas Chromatography.
• These properties allow FID high sensitivity and low noise.
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23. THERMAL CONDUCTIVITY DETECTOR
• Non-destructive universal detector
• Response depends on the thermal conductivity difference between the carrier gas
and the eluted components
• Responds to inorganic gases such as CO, CO2, NH3, CS2, etc.
• The advantages of TCDs are the ease and simplicity of use, the devices broad
application to inorganic and organic compounds.
• The greatest drawback of the TCD is the low sensitivity of the instrument in
relation to other detection methods, in addition to flow rate and concentration
dependency.
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25. ELECTRON CAPTURE DETECTOR
• Operation based on absorption of β – rays emitted by radioactive source Ni-63.
Specific detector, non-destructive in nature
• Widely used in environmental analysis e.g. organochlorine pesticide.
• The detector has a limited signal range and is potentially dangerous owing to its
radioactivity.
• The advantages of ECDs are the high selectivity and sensitivity towards certain
organic species with electronegative functional groups.
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27. TYPES OF DETECTORS WHICH ARE NEWLY
ADDED TO GC
• AED-Atomic emission detector
• GC-Chemiluminescence Detector
• Photoionization Detectors
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28. ATOMIC EMISSION DETECTOR
• Atomic emission detectors (AED), one of the newest addition to the gas
chromatographer's arsenal, are element-selective detectors that utilize plasma,
which is a partially ionized gas, to atomize all of the elements of a sample and
excite their characteristic atomic emission spectra.
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29. CHEMILUMINESCENCE DETECTOR
• Chemiluminescence detector (CD) is a process in which both qualitative and
quantitative properties can be determined using the optical emission from excited
chemical species.
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30. PHOTOIONIZATION DETECTOR
• Photoionization detector (PID) is a portable vapor and gas detector that has
selective determination of aromatic hydrocarbons, oregano-heteroatom, inorganic
species and other organic compounds.
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31. COLUMN EFFICENCY PARAMETERS
These include the following:
• Retention time
• Retention volume
• Separation factor
• Resolution
• Efficiency
• Asymmetry factor
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32. RETENTION TIME
• Time taken for the analyte to travel from the column inlet
to the point of detection.
• Time elapsed between sample introduction and
maximum of response, it is the characteristic time it
takes for a particular analyte to pass through the system.
K = tR – tm / tm
Where,
tR = unretained peaks retention time
tm = retention time of the peak of interest
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33. RETENTION VOLUME
• It is usually defined as the distance between the point of
injection to the peak maximum.
• It is the volume of the carrier gas necessary to elute the
solute of interest.
VR=FC * tR
• Where,
FC is the constant flow rate
tR is the retention time
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34. RESOLUTION AND EFFICIENCY
RESOLUTION:
• It is the measure of extent of separation of two
components and the base line separation achieved.
RS = 2 (Rt1 – Rt2) / w1 – w2
EFFICIENCY:
• Efficiency is related experimentally to solutes peak
width
where,
Rt = retention time
w = peak width at base
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35. ASYMMETRY FACTOR
• Chromatographic peak should be symmetrical about its center.
• If peak is not symmetrical –shows fronting and tailing.
• Fronting: due to saturation of stationary phase and can be avoided by using less
quantity of sample.
• Tailing: due to more active adsorption sites.
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36. DERIVATIZATION
• Derivatization is a technique used in chemistry which transforms a
chemical compound into a product (the reaction's derivate) of similar
chemical structure, called a derivative.
• A specific functional group of the compound participates in the derivatization
reaction and transforms to a derivate of deviating reactivity, solubility, boiling
point, melting point, aggregate state, or chemical composition to improve the
volatility and detectability to stabilize the analyte.
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37. APPLICATIONS
Pharmaceutical
• In the pharmaceutical industry GC is used to analyze residual solvents in both
raw materials (drug substance) and finished products (drug product).
• Biopharmaceutical applications include urine drug screens for barbiturates and
underivatized drugs and for ethylene oxide in sterilized products
Food/Flavors/Fragrances
• The food industry uses GC for a wide variety of applications including quality
testing and solvents testing.
• The Flavors and Fragrances industries use GC for quality testing and
fingerprinting of fragrances for characterization.
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38. Applications cont.…
Petrochemical
• GC applications include natural gas analysis or refineries, gasoline
characterization and fraction quantitation, aromatics in benzene, etc.
• Geochemical applications include mapping of oil reserves and tracing of
reservoirs etc.
Chemical/Industrial
• Chemical / Industrial uses include determination of product content, determination
of purity, monitoring production processes, etc.
• GCs are used to detect organic acids, alcohols, amines, esters, and solvents
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39. Applications cont.…
Environmental
• Environmental GC applications include detection of pollutants such as pesticides,
fungicides, herbicides, purge able aromatics, etc.
• Industrial environmental protection applications include stack and waste
emissions as well as water discharges.
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40. CONCLUSION
Gas Chromatography is one of the most important tools
in chemistry because of its simplicity, sensitivity and
effectiveness in separating components of mixtures. It is
widely used for quantitative and qualitative analysis of
mixtures and for the purification of compounds.
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41. REFERENCES
• Skoog, west, holler, & Crouch. Analytical chemistry: an introduction,7th edition.,
page no.667-682.
• Gurdeep R Chatwal & Sham K Anand. Instrumental methods of chemical
analysis, 5th edition).,2009, page no.2.673-2.700.
• Sharma BK. Instrumental methods of chemical analysis, 25th edition., Goel
publishing house, Meerut,2006, page no.3 - 23.
• Kaur H. Instrumental methods of chemical analysis, 6th edition., pragathi
prakashan, meerut,2010,page no.861 – 892.
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