The document summarizes a lab experiment using thin-layer chromatography to identify the components of an unknown analgesic drug tablet. The student grinded the tablet into a powder, dissolved it, and spotted it onto a TLC plate along with standards of aspirin, acetaminophen, caffeine, ibuprofen, and salicylamide. By calculating the retention factors and comparing them to the unknown spots, the student identified the unknown as containing aspirin and acetaminophen, matching the components of Excedrin. The purpose of identifying the unknown components was accomplished with minimal error.

1. Tanner Nielsen
CHMY 321­011
TA: Jeffrey Richards
11 September, 2015
Lab #1
Analyzing Drug Components Using Thin­Layer Chromatography
Introduction:
The purpose of the experiment was to identify the components of an unknown analgesic
drug tablet and identify the tablet as one of six possible commercial drugs. The six commercial
drugs were Advil, Anacin, Aspirin, B.C. Tablets, Excedrin, and Tylenol. Each drug contained 1
or 3 of these substances: Aspirin, Acetaminophen, Ibuprofen, Salicylamide, and Caffeine.
Thin­Layer Chromatographic Analysis was utilized in order to correctly identify the components
of the unknown analgesic drug. Knowing the components of the unknown allowed for the drug
to be identified as one of the six commercial drugs.
Thin­Layer Chromatography (TLC) was the method used to identify the drug. TLC is a
chromatography technique used to separate solutions. TLC is done on a plate that is coated with
a layer of absorbent material, in this case a silicone based material. After the solutions have been
spotted onto the plate, a solvent is drawn up the plate due to capillary action. Capillary action has
to do with the intermolecular forces between the liquid and surrounding solid surface. Different
substances ascend the plate at different rates which results in separation. The TLC in the
experiment used ethyl acetate/acetic acid (200:1) as the developing solvent. There were 6
solutions used as the analytes in the TLC. The solutions included: Aspirin, Acetaminophen,
Ibuprofen, Salicylamide, Caffeine, and the unknown drug solution which was created using the
powder from the drug and 1:1 ethanol/dichloromethane. After the TLC had been completed, the
retention factors of each spot were calculated. The Retention Factor (Rf) is calculated by the
distance traveled by the sample divided by the distance traveled by the solvent. The retention
factors of the 5 components were then compared to the unknown drug’s retention factors.

2. Knowing the components of the unknown analgesic , the drug was identified as one of the 5
commercial drugs.
Procedure/Observations:
List of Lab Materials:
Flat­Bladed Spatula
Small Test Tube
Stirring Rod
Filter­Tip Pipet
Small Vial
Silica­Gel TLC PLate
Micropipet
Pencil
Unique Tools:
Short­Wavelength (254 nm) Ultraviolet Light (do not look directly under lightsource)
Developing Chamber (containing a paper wick)
Chamber Cover
Silica­Gel TLC PLate
List of Chemicals:
Ethyl Acetate/Acetic Acid (200:1)
Quarter Tablet of Unknown Analgesic Drug
1:1 Ethanol/Dichloromethane

3. Acetaminophen
Salicylamide
Caffeine
Ibuprofen
Aspirin

4. (the chemicals were worked with under the fume hood)
First, ethyl acetate/acetic acid (200:1) was added to a developing chamber, containing a
paper wick, to a depth of about 5 mm. The chamber was then covered with a lid and put under
the fume hood. Next, a quarter tablet of the unknown analgesic drug was grinded into a powder
by using a flat­bladed spatula. The powder was grinded on a watchglass. The powder was then
carefully transferred to a small test tube. 2.5 mL of 1:1 ethanol/dichloromethane was then added
to the test tube containing the powder. The powder was dissolved as much as possible into the
solution by mixing the solid into the solvent using a stirring rod. Next, using a pipet that was
filled with cotton to act as a filter, the solution was transferred to a small vial. The solid was left
behind in the test tube. Next the 5 standard solutions of aspirin, ibuprofen, caffeine,salicylamide,
and acetaminophen were obtained. A starting line was created using a pencil. The 5 standard
solutions, along with the prepared unknown solution, were then spotted onto a silicon gel TLC
plate along the starting line. The spotting was done under the fume hood. The spots were labeled
as following right to left, acetaminophen, unknown F, salicylamide, caffeine, ibuprofen, and
aspirin. The aspirin spot was a little smaller compared to the others. A micropipet was used to do
the spotting. The micropipet was cleaned in between each spotting of a solution. The plate was
then placed into the developing chamber . Once the plate was developed, it was taken out of the
developing chamber and the solvent front was marked with a pencil. Once the TLC plate was
dry, the spots were observed under a short­wavelength (254 nm) ultraviolet light. The spots were
outlined with pencil and the centers where the intensity of the spot was the greatest was also
marked. The Rf values were then calculated using a ruler and a calculator. After the Rf values
were calculated, the active ingredients of the unknown were identified. They were identified by
comparing the Rf values for the known spots to the unknown spot. Using a table containing the
active ingredients of 6 commercial drugs, the unknown drug was identified by comparing its
components with those of the commercial drugs. The waste was then placed in the appropriate
waste bins.

5. Results:
Rf of Unknown F:
Spot 1: Rf= 1.2 cm/3.6cm = 0.33
Spot 2: Rf= 2.6 cm/3.6cm = 0.72
Rf of Acetaminophen:
Spot 1: Rf= 1.3 cm/3.6 cm = 0.36
Rf of Salicylamide:
Spot 1: Rf= 2.1 cm/3.6 cm = 0.58
Rf of Caffeine:
Spot 1: Rf= 0.3 cm/3.6 cm = 0.083

6. Rf of Ibuprofen:
Spot 1: Rf= 2.3 cm/3.6 cm = 0.64
Rf of Aspirin:
Spot 1: Rf= 2.5 cm/3.6 cm = 0.69
Discussion:
The retention factor can be used to identify components as each substance has its own
rate of travel due to the intermolecular forces between the solution and the surface of the TLC
plate. According to the results, the retention factor of aspirin was closest to spot 2 of the
unknown. Also, the retention factor of the acetaminophen was closest to spot 1 of the unknown.
Looking at the components of the 6 commercial drugs, the unknown was closest in identity to
Excedrin which contained aspirin and acetaminophen. The only error is that Excedrin also
contains a small amount of caffeine. There may have been caffeine in the unknown but the spot
was either not big enough or it was a personal mistake of not noticing it and marking it. However
Excedrin is the only commercial drug that contains both aspirin and acetaminophen. In
conclusion the unknown is most likely Excedrin.
Conclusion:
The purpose of this lab was to identify an unknown analgesic drug by using Thin Layer
Chromatography. The purpose was accomplished with minimal error. The unknown’s

7. components were identified by using TLC. Once the components were identified , the unknown's
components were concluded to best fit Excedrin. I was expecting the unknown to fit one of the 6
commercial drugs.
One way to create a more successful experiment is to make sure to clean the micropipet
fully before spotting each solution. This would be to avoid cross contamination, which would
make it harder to identify the spots. Also, it is important to make the spots spaced evenly and
sized equally to ensure maximum efficiency.