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 1: GC-MS Chromatogram of the hexane extract of the aerial parts of Fagonia

lonjispina

Figure 2 GC-MS Chromatogram of the ethyl ether extract of the aerial parts of Fagonia

lonjispina

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