The document discusses chromatography, a technique invented by Mikhail Tswett in 1901 to separate plant pigments. It covers the workings of gas chromatography, its instrumentation, and applications, highlighting its efficiency in analyzing volatile samples and its role in pharmaceutical quality control. Various types of chromatography and detectors used are also described.

2. CONTENTS:-
INVENTION OF CHROMATOGRAPHY
ABOUT CHROMATOGRAPHY
WORKING OF CHROMATOGRAPHY
INTRODUCTION OF GAS
CHROMATOGRAPHY
PRINCIPLE
THEORETICAL PLATE
INSTRUMENTATION
APPLICATIONS

3. Invention of Chromatography
Mikhail Tswett
Russian Botanist
(1872-1919)
Mikhail Tswett invented
chromatography in 1901
during his research on
plant pigments.
He used the technique to
separate various plant
pigments such as
chlorophylls, xanthophylls
and carotenoids.

4. Chromatography: (Greek = chroma “color” and
graphein “writing” ) Tswett named this new technique
chromatography based on the fact that it separated the
components of a solution by color.
Common Types of Chromatography
There are now several common chromatographic
methods. These include:
•Paper Chromatography
•Thin Layer Chromatography (TLC)
•Liquid Chromatography (LC)
•High Pressure Liquid Chromatography (HPLC)
•Ion Chromatography
•Gas Chromatography (GC)

5. How Does Chromatography Work?
In all chromatographic separations, the sample is
transported in a mobile phase. The mobile phase can be a
gas, a liquid, or a supercritical fluid.
The mobile phase is then forced through a stationary
phase held in a column or on a solid surface. The stationary
phase needs to be something that does not react with the
mobile phase or the sample.
The sample then has the opportunity to interact with the
stationary phase as it moves past it. Samples that interact
greatly, then appear to move more slowly. Samples that
interact weakly, then appear to move more quickly. Because
of this difference in rates, the samples can then be separated
into their components.

6. Gas Chromatography
It is based on distribution of gaseous solutes between a gas & liquid
or solid phase thus according to the nature of stationary phase they
are classified in two categories:-
Gas solid chromatography(SP-solid)
Gas liquid chromatography(SP-non volatile liquid on solid support)
PROPERTIES:-
 Good for volatile samples (up to about 250 oC)
 0.1-1.0 microliter of liquid or 1-10 ml vapor
 Can detect <1 ppm with certain detectors
 Can be easily automated for injection and data analysis

7. Principle
The organic compounds are separated
due to differences in their partitioning
behavior between the mobile gas phase
and the stationary phase in the
column.

8. The Theoretical Plate
Theoretical plate is a term coined by Martin &
Synge.
Theoretical plates (N) measure how efficiently a
column can separate a mixture into its components.
This efficiency is based on the retention time of the
components and the width of the peaks.

9. N = Number of theoretical plates (a measure of efficiency)
wb
tR
N = 16(
tR
wb
)2
tR is the retention time; it is measured from the injection peak
(or zero) to the intersection of the tangents.
wb is the width of the base of the triangle; it is measured
at the intersection of the tangents with the baseline.

10. Instrumentation of a Gas
Chromatography
Gas Supply: (usually N2 or He)
Sample Injector: (syringe / septum)
Column: 1/8” or 1/4” x 6-50’ tubing packed with
small uniform size, inert support coated with
thin film of nonvolatile liquid
Detector: TC - thermal conductivity
FID - flame ionization detector

11. Schematic of a Gas Chromatography

12. Our GC System
Carrier Gas : The main purpose of carrier gas is to
transport sample components through the column.(H ,
He , Ar & N are common carrier gases)
Injection Port : It is placed so that the sample is
introduced directly into the carrier gas.
Column :columns are of three type:-
•Packed column(PC)
•Open tubular column(OTC)
•Support coated open tubular column(SCOTC)
PACKED COLUMN : The column packed by the liquid
phase over an inert solid support.
OPEN TUBULAR COLUMN : It is about 100-130 fit
diameter about 0.01-0.03inch the inside wall of

13. in the form of thin & uniform film.
SUPPORT COATED OPEN TUBULAR COLUMN : columns
are made by depositing a micron size porous layer
of support material on the inside wall of a
capillaries columns & then coated with a thin film.
These column are of coarse having higher sample
capacity & yeild better resolution .
Detector : After resolution of solutes each is vapourised
components in turn from column & is carried into the
detector mixed with carrier gas.The detectors receive the
impulse from the elute of the column in the form of solute.
The vapour is sensed by the detectors it converts this
impulse into an electric signal proportional to the
concentration of the solute in carrier gas . The impulse
signal is emplified & recorded as a peak.
Various detectors are as follows:-
Thermal conductivity detector
Flame ionized detector

14. DDeetteeccttoorrss:: FFllaammee IIoonniizzaattiioonn
FID uses fuel mixed with
carrier and organic analyte.
Analyte forms ions in the
flame.
Cations from the flame are
gathered by the negative
electrode—produces a
current.
Advantage:inorganics do
not respond (He carrier gas),
so the low background signal
allows for LOD 100- to 1000-

15. Detectors: EElleeccttrroonn CCaappttuurree
Detects electronegative
atoms or groups (Cl, -NO2)
and also polynuclear
aromatics and conjugated
carbonyl compounds
These groups capture e–
that are produced from
nuclear radiation from 3H
Carrier gas hit by these
e– can release secondary e–,
which will be absorbed by
analyte
Has good LOD, but a
narrow linear range and

16. THERMAL CONDUCTIVITY DETECTOR (TCD)
A TCD detector consists of an electrically-heated
wire.The temperature of the sensing
element depends on the thermal conductivity
of the gas flowing around it. Changes in
thermal conductivity, such as when organic
molecules displace some of the carrier gas,
cause a temperature rise in the element which
is sensed as a change in resistance. The TCD
is not as sensitive as other detectors but it is
non-specific and non-destructive.

17. GAS CHROMATOGRAPHY (INSTRUMENT)

18. Applications
There are two type of analytical methods of gas
chromatography:-
•Qualitative Analysis
•Quantitative Analysis
QUALITATIVE ANALYSIS:-
This can be used to confirm identity of a suspected
compound but it along can not establish the structure of
unknown compound.
To supplement identification of the unknown by retention
data , suspected compound can be added to the suspected
compound & to see if there is a concomitent increase in the
peak heights.

19. QUANTITATIVE ANALYSIS:-
With the help of gas chromatography qualitative
analysis of individual component in a mixture.
The method has advantages over titrimetry or
spectrophotometry because both evaluations of a mixture
can be performed simultaneously.

20. There are numerous advantages of GAS
CHROMATOGRAPHY:-
Gas chromatography plays important role in the analysis of
pharmaceutical products & drugs.
It is used in quality control.
Analysis of new products.
In monitoring metabolites & biological fluids.
Few of application includes:-
•Antibiotics : penicillin
•Anti tuberculosis drugs : isoniazid
•Anti neoplastics : chlorambucil& florourasil
•CNS stimulants : caffine & theophyllin