This document discusses thin layer chromatography (TLC). It begins with an introduction explaining that TLC improved upon paper chromatography by allowing separations using a variety of solid adsorbents rather than just cellulose. The principles of TLC are described as compounds separating based on differing affinities to the stationary and mobile phases. Techniques including preparing the thin layer, selecting solvent systems, and developing the chromatogram are summarized. Applications of TLC such as separating inorganic and organic mixtures and its advantages over paper chromatography are highlighted. References conclude the document.

2. KUVEMPU UNIVERSITY
SIR M V GOVERNMENT SCIENCE COLLEGE
BOMMANAKATTE—BHADRAVATHI.
A SEMINAR TOPIC ON:
“Thin layer chromatography"
SUBMITTED TO ,
THE CHAIRMAN,
DEPARTMENT OF P.G STUDIES CHEMISTRY .
M.Sc., CHEMISTRY .
SUBMITTED BY,
ANUSHA V.S
Ist MSC-GC.

3. Thin Layer Chromatography

4. INDEX
• Introduction
• Principle
• Techniques of TLC
• Applications of TLC
• Conclusion
• reference

5. INTRODUCTION
Paper chromatography has been applied to isolate and
identify a wide variety of organic and inorganic substances.
But its use is limited by the fact that separations can be
carried out only with fibrous materials such as cellulose.
In 1956, Egon Staul developed the equipment for
reproducible TLC and showed its wide applicability.
The later chromatography can Be defined as a method of
separation or identification of a mixture of components into
individual component by using finely divided absorbent (solid
/ liquid) over a glass plate and liquid as a mobile phase.

6. PRINCIPLE
TLC depends on the separation principle. The separation
realise on the relative affinity of compounds towards both the
phases.
The compounds in the mobile phase move over the surface of
the stationary phase the movement occurs in such a way that
the compounds which have a higher affinity to the stationary
phase move slowly while the other compounds travel fast.
Therefor, the separation of the mixture is attained,on
complition of the separation process the individual
components from the mixture as spots at respective levels on
the plates.
Their character and the nature are identified by suitable
detection techniques.

7. Technique of TLC
1. Adsorbents
Silica gel, Kieselguhr, alumina, modified cellulose
powders, polyamide powder, magnesium silicate, calcium
silicate, etc. may be used.
2. Slurries
The slurries are normally made in water which may
contain acids, bases, buffers or complexing agents for
specific separations. Some organic solvents can also be
used.

8. Technique of TLC
1. Adsorbents
Silica gel, Kieselguhr, alumina, modified cellulose
powders, polyamide powder, magnesium silicate, calcium
silicate, etc. may be used.
2. Slurries
The slurries are normally made in water which may
contain acids, bases, buffers or complexing agents for
specific separations. Some organic solvents can also be
used.

9. 3. Preparation of thin layers on plates
i. The usual procedure is to place two clean microscope
slides together to make a double thickness of glass.
ii. Dipping : Dip the two slides together into the slurry. The
two slides are then withdrawn, dried, and separated. The
slides are now ready for the preparation of chromatogram.
iii. Mechanical spreading: In one method the adsorbent
reservoir containing the slurry is held stationary and the
plate to be coated is moved underneath.
In the other method the reservoir is moved over the plate.
The layer thickness of 0.25mm is most satisfactory.

10. 4. Chromatoplates
In TLC the adsorbent supports are usually glass plates of
square or rectangular shape.
Synthetic polymers, such as polyethylene terephthalate or a
metal foil can also be used as support.
Pre-coated plates or plastic sheets are now available.
5. Activation of adsorbent
The water or other polar solvents, which greatly affect the
development of chromatogram, should be removed from the
chromatoplates. This is known as activation.
Sometimes, the dry chromatoplates are exposed to the
atmosphere because a certain amount of moisture is essential
for satisfactory resolution. This process is called deactivation.

11. 4. Chromatoplates
In TLC the adsorbent supports are usually glass plates of
square or rectangular shape.
Synthetic polymers, such as polyethylene terephthalate or a
metal foil can also be used as support.
Pre-coated plates or plastic sheets are now available.
5. Activation of adsorbent
The water or other polar solvents, which greatly affect the
development of chromatogram, should be removed from the
chromatoplates. This is known as activation.
Sometimes, the dry chromatoplates are exposed to the
atmosphere because a certain amount of moisture is essential
for satisfactory resolution. This process is called deactivation.

12. 6. Selection of solvent
The choice of solvent depends on two factors:
i. The nature of the substance to be separated, and
ii. The nature of the adsorbent.
The common procedure is to match the polarity of the
solvent to that of the substances being separated.
For polar substances – Polar solvents,
For Non-polar substances – Non-polar solvents, and
For less polar substances – mixture of polar and non-polar
solvents should be used.
It has been observed that a combination of two solvents
gives better separation than obtained with a single solvent.

13. 7. Sample application
Using a fine capillary tube or a micropipette the samples are
applied in small spots to the baseline about 2.5 cm from one
edge of the plate and at least 1 cm apart.
The solvent is evaporated between applications by directing a
stream of warm air from a drier.
Commercial applicators are also available with which it is
possible to apply a very narrow, uniform spot along the length
of the chromatoplate.
Chromatographic standards are also applied beside the
sample.
The chromatoplate is now ready for development.

14. 8. Development of the chromatogram
Ascending method
The development of the chromatogram is usually carried out
by ascending method in a specially designed developing
chamber or tank.
After a certain time when the solvent has moved to about 10-
15 cm above the origin, the plate is removed from the tank
and the solvent front is carefully marked with a sharp pencil.
Other methods: Horizontal development, descending
development, continuous flow development and two-
dimensional development are also used.

15. Lid
Chromatoplate
Baseline
Solvent
Apparatus for thin layer chromatography

16. Applications of TLC
1. Separation of inorganic ions
TLC has been used for separating cationic, anionic, covalent
species and organometallic compounds.
2. Application in organic chemistry
TLC has been used widely for isolation, purification and
identification of individual components in a mixture.
i. For checking purity of samples
ii. Examination of completeness of reaction
iii. For identifying compounds
iv. For the separation of acids, alcohols, glycols, amines, etc.

17. It gives improved resolution and compact spot.
It is applicable to the analysis of thermally labile
compounds. It is more sensitive and gives sharper
zones.
TLC plates can be heated to high temperatures without
causing any damage to it.
The capacity of thin layers of an adsorbent is higher
than that of paper.
CONCLUSION

18. REFRENCE
ANALYTICAL CHEMISTRY
Author – Gary .D.christian
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