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TLC Analysis of Analgesic Drugs

This document summarizes an experiment using thin layer chromatography (TLC) to analyze unknown analgesic drug samples. Reference drugs including acetaminophen, aspirin, caffeine, ibuprofen, and naproxen sodium were run on silica plates along with two unknown samples. The plates were developed in ethyl acetate and glacial acetic acid solvent and visualized under UV light and iodine vapor. The Rf values were calculated and compared to determine that unknown sample 1 was acetaminophen and unknown sample 2 was naproxen sodium. Possible sources of error included contamination during spotting or an unstable developing chamber.

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arshdeep kaur
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194 views6 pages

TLC Analysis of Analgesic Drugs

This document summarizes an experiment using thin layer chromatography (TLC) to analyze unknown analgesic drug samples. Reference drugs including acetaminophen, aspirin, caffeine, ibuprofen, and naproxen sodium were run on silica plates along with two unknown samples. The plates were developed in ethyl acetate and glacial acetic acid solvent and visualized under UV light and iodine vapor. The Rf values were calculated and compared to determine that unknown sample 1 was acetaminophen and unknown sample 2 was naproxen sodium. Possible sources of error included contamination during spotting or an unstable developing chamber.

Uploaded by

arshdeep kaur
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Noordeep kaur

Chem 112-A-01
Oct 08,2018
Experiment 10:TLC Analysis of Analgesic Drugs
qPurpose of the experiment:​The main objective of this experiment is to find the
unknown drug by TLC comparison with several known drugs given in the table below
and using them as a reference to investigate the purity of unknown compound using
column chromatography.
Chemical Used:

Reference Plate Molecular Sample Plate Molecular


structure Structure

Acetaminophen Naproxen Sodium


(Ac) (Nap)

Aspirin (Asp) 10% Glacial Acetic


Acid

Caffeine (Cf) Ethyl acetate

Ibuprofen (Ibu) Unknown Sample


1
Salicylamide (Sal) Unknown Sample
2

Reference mixture Reference mixture


(Rf) (Ref)
Apparatus:
Procedure:​1.Prep the plate according to instructor advice.
2.Place plate on eat time in developing chamber.
3. Use 0.5% glacial acetic acid in ethyl acetate as your solvent.
4.Develop the plate and remove after solvent has reached almost top (leaving only few
mm from top)
5.Air dry and visualized under UV and then use iodine vapors for confirmation of your
unknown compounds.

Safety Hazard: ​Carefully handle silica gel plates,all the chemicals used may cause
irritant if excess swallowed.Do Not look directly under UV light as it damage eyes.Do
not inhale iodine vapour directly.
Data Table:

Silica gel plate Under UV Silica gel plate after Rf value


light immersed in iodine
vapor

Rf (Asp) = 0.9 cm
Rf (Cf) = 0.28 cm
Rf ( Nap) = 0.9 cm
Rf (Ref) = 0.14 cm
Rf (Ibu) = 1 cm
Rf (Ac) = 0.710 cm

Rf ( unknown sample 1 ) =
0.76 cm
Rf ( unknown sample 2 ) =
0.9 cm
Three silica plate are made.Each have following chemicals.

Calculations:
Rf value = Distance travelled by compound (cm) / Distance travelled by solvent
(cm)
Rf (Asp) = 6.3 cm / 7 cm = 0.9 cm
Rf (Cf) = 2 cm / 7 cm = 0.28 cm Plate 1
Rf ( Nap) = 6.9 cm / 7 cm = 0.9 cm
Rf (Ref) = 4.5 cm /6.9 cm = 0.14 cm
Rf (Ibu) = 6.9 cm / 6.9 cm = 1 cm Plate 2
Rf (Ac) = 4.9 cm /6.9 cm = 0.710 cm

Rf ( unknown sample 1 ) = 5 cm /6.6 cm = 0.76 cm


Rf ( unknown sample 2 ) = 6 cm /6.6 cm = 0.9 cm Plate 3

Conclusion and Discussion:


From the experiment it can be concluded that unknown sample 1 is Acetaminophen
(Ac) and unknown sample 2 is Naproxen sodium (Nap) from the Rf value..The glass
plate made up of silica gel is highly polar in nature. Chemical compound that are more
polar in nature will remains at stationary phase and weakly polar substances will enter
in mobile phase.These non polar compounds will have less attraction to solvent and
move quickly with eleunet. Rf value of caffeine is very small and Rf value of ibuprofen is
large as compare to other chemical compounds.Possible source of error can be
contamination of capillary while spotting the sample. Large spot result in intermixing of
chemical compounds and developing chamber being disturbed may alter the result.
Post Lab Questions:
Q1.What happens if the spots are made too large when preparing TLC plate for
development?
Sol: ​Too large spot can result in mixing of chemical compounds with one another which
result in contamination and alter the experimental values.
Q2. What happens if spots are made too small when preparing TLC plate for
development?
Sol: ​Too small spot might not give us accurate results as there would not be enough
components in the mixture to separate and it will not be able to reach to mobile phase ​Q
3. Why must the spots be above the level of development solvent in the
development chamber?
Sol​: If the spots are below the level of development solvent then they will be dissolved
completely by the solvent and nothing will go up through the columns.
Q4. What would happen if the spotting line and positions were marked on the
plate with a ballpoint pen?
Sol: ​Pen has its own dye and it can mix with compounds and get separate. This is why
we used a pencil for the experiment.

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