WILL BE PRESENTED BY:

GAS CHROMATOGRAPHY

RAHAT INAYAT ALI – 14CH23

Contents Of Topic

HistoryIntroductionPrincipleTheoryInstrumentation Carrier Gas Flow Regulator Flow Meter Columns Injection System DetectorsAdvantages and Disadvantages

Inventor of Chromatography

Mikhail Tswett (Russian Botanist), Invented Chromatography in 1901, During his research on plant pigments.

He used the technique to separate, various plant pigments such as:

Chlorophylls Xanthophylls Carotenoids.

1872-1919

Introduction

It is an analytical technique, used for separation of Thermal stable and volatile substances.

Mobile Phase Gas Stationary Phase Solid or Liquid

Principles

Adsorption or Depends on the

StationaryPartition Phase used.

If Stationary phase is:Liquid -> Gas Liquid Chromatography-> Partition PrincipleSolid -> Gas Solid Chromatography-> Adsorption Involved.

In general, compounds with low boiling points (High Vapor Pressures) spend more time in the Mobile Phase and elute from the column in a shorter amount of time than compounds with High Boiling Points.

Theory

The component to be separated from Gas Chromatography should be:

Volatile and Thermo stability.

Instrumentation

Carrier GasFlow RegulatorFlow MeterInjection DeviceColumnsTemperature Control DeviceDetectors

Working Of Gas Chromatography

Carrier Gas The mobile phase or moving phase is a carrier gas,

usually an inert gas. Such as Helium or an unreactive gas such as Nitrogen.

Note: Probably more than 90% of the present GC instruments run with Helium as a carrier gas. Some use Hydrogen and Nitrogen as well.

Hydrogen-> Adv: Better thermal conductivity, Low density. DisAdv: Reacts with unsaturated compounds, and it is inflammable.Helium-> Adv: Excellent thermal conductivity. DisAdv: Expansive.Nitrogen-> Adv: Inexpensive.DisAdv: Reduced sensitivity.

Flow Regulator As carrier gases stored under high pressure, Flow

regulator are used to deliver the Gas with uniform pressure or flow rate.

Flow Meter Rotameter It is conveniently before the column inlet. It has an

ordinary glass tube like burette with a float held on to the spring, the level of the float is determined by the flow rate of the carrier gas and is precalibrated.

ColumnMade of Glass or Metal, such as Stainless Steel. Stainless steel-> Long life, can be handled easily and it

reacts with some compounds. Glass-> Widely used, as they are inert but highly fragile.Column can be used both for preparative and analytic purposeTypesPacked Column->GSC:Packed with graded adsorbnt or porous polymer.GLC: Packed with liquid phase coated graded inert solid support.Open Tubular Column->Made of stainless steel with long capillary

tubing in length and have uniform, narrow internal diameter, know as Capillary of Golay column.

Support Coated Open Tubular Column-> Improve version of OTC.

Injection System Injected by Hypodermic Syringe from rubber

septum

A Hypodermic needle is used for rapid delivery of liquids.

Detectors

Detectors

Advantages:Relatively inexpensive to acquire and operate.Low maintenance requirement.Linearity and detection ranges: FIDS can

measure Organic substances concentration at very low and very high Levels.

DisAdvantages: Can not differentiate b/w different Organic

substances. They also can not detect Inorganic substances.

To ask a Question.. It signals the illiteracy there….

ANY QUESTION ??????? Hmm….?

Thanks To All ……

Special Thanks To Sir Zulfiqar Ali Solangi