what is gas chromatography assignment
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My lecturer assign us to do assignment about gas chrmatography during our final years in diplomaTRANSCRIPT
What is Gas Chromatography?
Gas chromatography or gas-liquid chromatography is a chromatographic
technique that used for the separation of volatile organic compound. It
involves separation, identification and quantification of the chemical
compound. The separation of the mixture is done due to the difference in
the interaction between the analyte with stationary phase as it carries by
the mobile phase. The chemical compounds or analyte where in vapour
state is distributed between the stationary phase and the mobile phase.
The mobile phase does not interact with molecule of the analyte; its only
function is to transport the analyte through the column. In this
instrumentation of chromatography, the mobile phase is gas while the
stationary phase is liquid that held inside the column. There were few
components that made up gas chromatography which is carrier
gas(mobile phase), injection system, oven(where stationary phase
located), column, detector and signal processing and read out.
Components of gas-liquid chromatography
(from http://teaching.shu.ac.uk)
1. Mobile phase:
Mobile phase must not react with the analyte. Its function is to carry
analyte through the stationary phase or the column. It also refers as
carrier gas.
- Carrier gas
It must be chemically inert, for example helium, nitrogen, and
hydrogen. Pressure regulators, gauges and flow meter were
associate with the gas supply. It usually contain molecular sieve
to remove water or other impurities.
2. Sample injection system.
It is where the sample is being introduced to the system. Column
efficiency requires that the sample to be of suitable size and
introduced as a plug of vapor. A Slow injection of oversized samples
will causes results to have a band spreading and poor resolution.
Commonly used method for injection of sample is by the aid of
microsyringe to inject a liquid or gaseous sample through a self-
sealing, silicone-rubber diaphragm or septum into a flash vaporizer
port located at the head of the column where the sample port is
ordinarily about 50oC above the boiling point of the least volatile
component of the sample. Thus before running the sample, it is
crucial to know the boiling point of the analyzed sample. There are
few types of injection port that is used which is flash vaporization,
splitless capillary injector that is commonly used, direct injector that
used in trace analysis, cool on-column injector, autosampler and
head space.
3. Oven
In gas chromatography, optimum temperature depends on the
boiling points of the sample components. Thus the control of the
temperature depends on the type of compound analyzed which is its
boiling point. A temperature that is roughly higher than the average
boiling point of the sample results in a reasonable elution period.
Temperature programming is used to reduce the retention time of
the sample in the column and overcome seperations problem.
4. Column
It is where the stationary phase of the system located. Column is
the location where separation of the analyte occurs. There are two
types of column in gas chromatography which is packed column and
capillary column.
- Packed column:
It is less commonly used and made of glass and steel. It length
range from 1 to 5 meter with internal diameter if 2 to 4 mm.
These column is densely packed with uniform, finely divided solid
support, coated with thin layer (0.05 to1μm) of stationary liquid
phase. It also accommodate larger samples. Inside the packed
column, the carrier gas flow between 10 – 40 mL/min. However, it
is not suitable for trace analysis. It also contain an inert and
stable porous support on which the stationary phase can be
impregnated or bound.
- Capillary column
Unlike packed column, capillary column is widely used in gas
chromatography analysis. It also known as open tubular calumn.
Its length is between 10 and up to 100 meter. They were coiled
around a light weight of metallic support. There were a few types
of capillary column which is:
FSOT (Fused Silica Wall Coated).
Its internal diameter range from 0.1 to 0.3 mm
WCOT (Wall Coated)
Internal diameter range from 0.25 to 0.75 mm
SCOT (Support Coated)
Its internal diameter is 0.5 mm
PLOT
5. Detector
It measure the eluents after as they evolve from the column. It is
where the components of mixture or analyte is identified. There
were few factors that made up a good detector.
For ideal detector:
a) it need high reliability & ease to use.
b) Similarity response toward all solutes or alternatively a high
predictable and selective response toward one or more classes of
solute.
c) Detector should also be nondestructive where there is no
damage to column is occur.
d) High sensitivity
e) Have a good stability and reproducibility.
f) Linear response to solutes that extends over several orders of
magnitude.
g) Temperature range from room temperature to atleast 4000C.
There are three types of detectors that is used in gas
chromatography:
a) Thermal conductivity detector(TCD)
It is a nondestructive universal detector. That has a moderate
sensitivity. It is less satisfactory with carrier gas whose
conductivities closely resemble those of most sample components.
It measure change in thermal conductivity.
b) Flame Ionization Detector (FID)
It is destructive one. Combustible organic compound is needed for
this type of detector. It is very sensitive and have wide dynamic
range. The signal is depend on number of carbon atom in the
organic analyte. It is mass sensitive instead of concentration
sensitive. It is not sensitive to noncombustible analyte such as water
and carbon dioxide gas.
c) Electron Capture Detector (ECD)
It is non-destructive detector. It measures the changes in electron
flown from source as eluting compound is capturing the electron. In
the absence of organic species, the result is a constant standing of
current. In the presence of organic molecules containing
electronegative functional groups that tend to capture electrons,
results in the current decreases markedly.
6. Signal processor and read out
The data from the experiment will be displayed.It displays the peaks
of all the substances in the sample. This is called the
chromatogram. Software can perform all the calculations.
Application of Gas- Liquid Chromatography
GC-MS ANALYSIS OF ETHANOL EXTRACT FROM THE AERIAL PARTS
OF FAGONIA LONGISPINA (FAMILY ZYGOPHYLLACEAE)
Apparatus and material:
GC Clarus 500 Perkin Elmer equipment, Aerial parts of Fagonia longispina,
60% EtOH, distilled water, hexane, ethyl ether, chloroform. (100%
Dimethylpolysiloxane). 100% Dimethylpolysiloxane
Method:
Preparation of the extracts
1. 100 g dried powder of the aerial parts of Fagonia lonjispina
extracted by using 60% EtOH.
2. The extraction is concentrated. Then diluted with water and
partitioned with hexane, ethyle ether and Chloroform.
3. The residue of the hexane extract which is 2 gram, of the ethyl
ether extract with 1.4 gram and of the 1.6 gram CHCl3 extract were
performed using a gas chromatograph-mass spectrograph (GC-MS).
Gas Chromatography Mass Spectrometry Analysis
1. Analysis performed by using GC Clarus 500 Perkin Elmer equipment.
2. Compounds were separated on Elite-1 capillary column (100%
Dimethylpolysiloxane).
3. Oven temperature was programmed at 100ºC for 1 min, then
increased to 220ºC at the rate of 10ºC/min, then increased up to
260ºC at the rate of 5ºC/min which is for 9 min.
4. Ionization of the sample components was performed in the EI mode
(70 eV).
5. The carrier gas was helium (1ml/min) and the sample injected was
2 μl.
6. The detector was Mass detector turbo mass gold-Perkin Elmer.
7. The total running time for GC was 28 min and software used was
Turbo mass 5.2. The individual constituents were identified by
comparing their mass spectra with the spectra of known compounds
stored in the spectral database,NBS,WILEYand NIST attached to the
GC-MS instrument and reported.
Expected Results:
Figure 3 GC-MS Chromatogram of the Chloroform extract of the aerial parts of Fagonia
lonjispina
Conclusion:
The analysis of the phytochemicals in the hexane, ethyl ether and
chloroform extracts of Fagonia lonjispina aerial parts revealed 13
compounds namely that major players in antioxidant responses evoked by
the plant.
List of compound present.
Ethyl Palmitate (26.71%), 9,12Octadecadienoic acid, ethyl ester( 16.03
%), 9.12.15 Octadecatrienoic acid,ethyl ester(z,z,z) (57.25%) , Phenol2,6-
bis (1,1-dimethylethyl)-4-methyl- ( 27.21%) , N-hexadecanoic
acid( 12.24%), Tridecanoicacid ( 9.25%), 9,12-
Octadecadienoicacid(z,z) ,methylester ( 8.16%), 11,14,17 –
Elcosatrienoicacid,methyl ester ( 34.69%) , Decanoic acid ( 12.24) , 9-
Elcosene,( E ) ( 15.62%) , Cyclotetracosane ( 03.75%), 1-Heptadecene
( 23.12%), 1-Nonadecene ( 06.25%) .
UNIVERSITI TEKNOLOGI MARA SABAH
FACULTY OF APPLIED SCIENCE
DIPLOMA IN SCIENCE
CHM260 CHAPTER 5
GAS-LIQUID CHROMATOGRAPHY
TITLE : GAS CHROMATOGRAPHY, COMPONENTS AND APPLICATION
NAME : Ahmad Ismi Zulfadli Bin Ishak
Matrix ID : 2010852022
GROUP : AS1206A1
DATE : 11th March 2013
LECTURER : MISS NOOR EZAWANIEE HJ MOULTON