INTRODUCTION

Name: SADOON ALI ZAHID

Registration #:529-FBAS/BSBT/F13

Subject: Pharmaceutical Chemistry

Topic: Gas Chromatography (G.C)

OUTLINES

Chromatography

Types of Chromatography

History

Gas Chromatography (G.C)

Gas Chromatography main components

Working principle of Gas Chromatography

Procedure of Gas Chromatography

Factors affecting Gas Chromatography

Advantages of Gas Chromatography

Application of Gas Chromatography

Conclusion

Chromatography

Greek words “CHROMA” and

“Graphein”.

Process of separation and

analyzation of complex mixture.

Chromatography is a great

physical method for observing

mixtures and solvents.

How it works?

It works on the basis of rate at

which the types of components

flow. As the mixture of various

components enter the

chromatograph we will observe

that the different components of

a mixture move/flow at different

rate. This different rate of flowing is

responsible for the separation of

their components.

Types of Chromatography

History

FRITZ PRIOR

Gas Chromatography

Gas chromatography is separation method.

Gas chromatography isa chromatographic technique thatcan be used to separate volatileorganic compounds.

Gas Chromatography consists oftwo phases.

Mobile Phase

Stationary phase

GAS CHROMATOGRAPH MAIN COMPONENETS:

Carrier Gas

Injection Port

Column

Oven

Detector

Sample

CARRIER GAS

This is the mobile phase and

should be inert gas(He, Ar, H2,

N2 etc.)

INJECTION PORT

The injection port consist of

rubber septum through which a

syringe needle is inserted to

inject the sample.

COLUMN

Column is the most important

component where separation

takes place.

OVEN

Oven is also an important

component in which column is

fitted.

DETECTOR

Detector is to indicate the

presence and measure the

amount of component eluted

out from the column.

SAMPLE

The mixture of components

which is to be analyzed.

Properties of carrier Gas The carrier gas must be chemically inert.

Commonly used gases include nitrogen,

helium, argon, and carbon dioxide.

The choice of carrier gas is often dependant

upon the type of detector which is used.

The carrier gas system also contains a

molecular sieve to remove water and other

impurities.

- P inlet 10-50 psig

Column Types

There are two general types of

column, packed and capillary (also known

as open tubular).

Packed columns contain a finely divided, inert,

solid support material ( diatomaceous earth)

coated with liquid stationary phase. Most

packed columns are 1.5 - 10m in length and

have an internal diameter of 2 - 4mm.

Capillary columns have an internal diameter of

a few tenths of a millimeter. They can be one of

two types; wall-coated open tubular (WCOT)

or support-coated open tubular (SCOT).

Ideal GC-Detectors

Sensitive (10-8-10-15 g solute/s)

Operate at high T (0-400 °C)

Stable and reproducible

Linear response

Wide dynamic range

Fast response

Simple (reliable)

Nondestructive

Uniform response to all analytes

WORKING PRINCIPLE OF GC

It works on the principle that the

organic compounds are separated

due to differences in their

partitioning behavior between

Mobile phase and Stationary

phase.

The mobile phase is comprised of

inert gas.

The stationary phase consists of

packed column.

PROCEDURE OF GC

Sample is injected in column.

Oven heats the system to vaporize

the sample and speed its passage

through the column.

The different components of the

sample will be separated by the

column because each of the

components “sticks” to the liquid

coating that on the column

packing differently.

PROCEDURE OF GC

When a substance leaves the

column, it is sensed by a detector.

The detector generates the voltage

that is proportional to the amount of

the substance.

Chromatogram

FACTORS AFFECTING GCTemperature: The higher the

temperature, the more of the

compound is in the gas phase.

Carrier gas flow: If the carrier

gas flow is high, the molecules do

not have a chance to interact with

the stationary phase.

Column length: The longer the

column is the better the separation

usually is.

Amount of material injected:

The injection of too much

sample causes poor

separation.

Effective Factor: High

temperatures and high flow

rates decrease the retention

time, but also deteriorate the

quality of the separation.

Applications Miscellaneous-analysis of foods like carbohydrates,

proteins, lipids, vitamins, steroids, drug and pesticides

residues, trace elements

Pollutants like formaldehyde, carbon monoxide, benzene, DDT etc.

Dairy product analysis- rancidity

Separation and identification of volatile materials,

plastics, natural and synthetic polymers, paints, and microbiological samples

Inorganic compound analysis

Advantages

The technique has strong separation power and even complex

mixture can be resolved into constituents

The sensitivity of the method is quite high

It gives good precision and accuracy

The analysis is completed in a short time

The cost of instrument is relatively low and its life is generally long

The technique is relatively suitable for routine analysis

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.