Chemistry Lab Report: Separation of Analgesics and Analysis

This lab report details an experiment on the separation of analgesics (paracetamol and caffeine) using thin-layer chromatography (TLC). The report begins with an introduction to the objective of separating key analgesics and identifying ingredients using TLC. The results section presents the observations from the TLC plate, including the movement of paracetamol and caffeine in different samples (A, B, and C) and the calculation of Rf values. The report also includes a graphical representation of the retention values. The discussion section explains the principles of separation based on molecular interactions, polarity, and solubility. It summarizes the compounds present in each sample, discusses the procedure (sonication, use of ethyl acetate, and NaOH), and explains how different factors affect retention values. The conclusion affirms the results based on theory, and the report includes a bibliography citing relevant sources on solubility and analgesic properties.

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Lab Report
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Lab report

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Lab Report
Separation of analgesics
Results and graph
From the results on the Thin layer chromatography plate (TLC) after elution, it is observed that
the paracetamol was present in sample A and sample C, since the dot presence of Paracetamol
moved 2.7 cm above the base line according to its solubility with the Methanol, temperature and
pressure.
Similarly, Caffeine was present in sample A and sample B, since the solvent of the Caffeine
through capillary moved up to 4.5 cm which is similar to the second dot of sample A that is
noted on the TLC.
The Rf Values
Rf (Retention Value) value is defines as the reaction of the distance moved by solute and
the distance moved by the solvent along the chromatography paper1.
Solvent front
z
y
baseline
Rf = Y
Z
1solubility of paracetamol in pure solvent. Journal of chemical and engineering data 44(6

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Lab Report
From the respective results
Baseline
Sample A
Rf = 2.7
6.7 = 0.403
And
Rf = 4.5
6.7 = 0.672
Sample B
Rf = 4.5
6.7 = 0.672
Sample c
Rf = 2.7
6.7 = 0.403
Paracetamol
Rf = 2.7
6.7 = 0.403
Caffeine
A B C P C
2.7
1.5
cm
4.5
2.7cm
Solvent line
4.5
cm

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Lab Report
Rf = 4.5
6.7 = 0.672
COMPOUNDS A B C P C
Rf 0.403
0.672
0.672 0.403 0.403 0.672
Another factor that will determine the position or movement of the samples on the TLC is the retention
value, which has been calculated as shown above.
It is observed that Rf of sample A, sample C and Paracetamol are same, which is equal to 0.403 while the
retention value of second dot of sample A and Caffeine are 0.672, this confirms that there is presence of
Caffeine in sample A and sample B, while there is presence of Paracetamol in samples A and C.
Graphical presentation of Retention value(Rf) against the drugs
sample A sample B sample C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Paracetamol
caffeine
drugs
Rf
There is presence of Paracetamol and Caffeine in the sample A, presence of Caffeine in sample B and
presence of Paracetamol in sample C.

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Lab Report
Discussion
The objective of this experiment was;
i. To separate key analgesics from the tablets by manipulating the physiochemical
properties.
ii. To experience of using thin layer chromatography to identify the presence of ingredients.
From this objective and the experiment carried out to achieve them it can be summarized that
Caffeine and the Paracetamol depends on their molecular interaction with the chromatography
plate and mobile phase which will adhere to the plate more or less than the other compounds as
per its polarity, in this case paracetamol will be attracted close to the baseline since it is more
polar than Caffeine, hence allowing quick and efficient separation of the two.
The thin layer chromatography clearly shows by determining that;
i. Compound in sample A contains both Caffeine and the paracetamol
ii. Compound in sample B contain Caffeine
iii. Compound in sample C contain paracetamol
In addition, from the procedure ( b) the tablet was placed in ethyl acetate and then sonicated.
During sonication, ultrasound waves broke apart the intermolecular bonds holding compounds
together and separating them into individual molecules. Both paracetamol and caffeine dissolved
in the ethyl acetate and the solid that was left behind was the excipients that were present in the
tablet that were not soluble in the ethyl acetate.
Sample A will contain both paracetamol and caffeine, since they are both unionized polar
molecules, hence they are soluble in the ethyl acetate.
The addition of Sodium hydroxide ( NaOH) neutralizes the Hydrochloric acid ( HCl), this helps
in ionizing the paracetamol while making caffeine unionized, the impurities of sodium chloride
formed are then separated by adding more ethyl acetate. It should be noted that caffeine is
soluble in the ethyl acetate and so the two layers will be separated to leave pure caffeine and
since the Sodium hydroxide is in excess the solution becomes alkaline.
The small portion of the of the Paracetamol during its separation using the separating funnel will
be contained in the solution, where the addition of ethyl acetate will react with all the
Paracetamol hence leaving behind sample B that contains Caffeine2.
In procedure ( e) addition of sodium hydroxide ( NaOH) neutralizes HCl and ionize the
paracetamol, and become insoluble in ethyl acetate, addition of hydrochloric acid lowers the PH
and unionize the paracetamol and makes it soluble with ethyl acetate, the ethyl acetate will help
in separating the paracetamol from the sodium chloride impurities, hence sample C will be
2 caffeine accelerates absorption and enhances the analgesic effect of acetaminophen. The Journal of Clinical
Pharmacology, 47(6)

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formed, it is observed to contain presence of Paracetamols as shown on the thin layer
chromatography plate.
It should be noted that the three samples A, B and C, in inclusion of Paracetamol and Caffeine
will have different retention value, since the retention values depends on;
i. The boiling point of the compounds, where substance with a higher boiling point will
have a long retention time because of its longer time of condensation.
ii. The solubility of the liquid phase, where a compound with a higher solubility will
have a higher retention time. The TLC plate is coated in silica gel which is very
polar, and any polar molecules will be attracted to the silica gel during the
stationary phase. The more polar a compound, the more attracted that compound
will be to the surface of the TLC plate and therefore travel less distance during the
mobile phase that less polar compounds3
iii. The temperature, where a higher temperature will result to a shorter retention time.
In conclusion, it can be concluded that the results are as per the theory where alteration of the
results can only be obtained when the factors affecting the retention values are also altered or
changed, also there will traces of paracetamol in sample B. this could be due to errors when
separating them or even that the ratio of paracetamol could be far greater than caffeine
Bibliography
1.
Granberge R.A, R. A., 1999. solubility of paracetamol in pure solvent. Journal of chemical and
engineering data 44(6), pp. 1391-1395.
2. Renner, B., Clarke, G., Grattan, T., Beisel, A., Mueller, C., Werner, U., Kobal, G. and Brune, K., 2007.
Caffeine accelerates absorption and enhances the analgesic effect of acetaminophen. The Journal of
Clinical Pharmacology, 47(6), pp.715-726.
3. Shalmashi, A. and Golmohammad, F., 2010. Solubility of caffeine in water, ethyl acetate, ethanol,
carbon tetrachloride, methanol, chloroform, dichloromethane, and acetone between 298 and 323 K.
3Solubility of caffeine in water, ethyl acetate, ethanol, carbon tetrachloride, methanol, chloroform,
dichloromethane, and acetone between 298 and 323 K. Latin American applied research, 40(3)

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Latin American applied research, 40(3), pp.283-285.