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Lab report content:
Objective
Materials (a) chemicals (b) equipments
Methods
Results
Discussion
Conclusion
References
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Methods
Results
Discussion
Conclusion?
References?
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Lab report content:?
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Materials (a) chemicals (b) equipments
Methods
Results
Discussion
Conclusion?
References?
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Materials (a) chemicals (b) equipments
Methods
Results
Discussion
Conclusion?
References?
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Experiment conducted on Feb 25th, 2022.
Instructor: Professor Shanshikanth Ponnala

Chemistry 230-085B
Nicola Poyotte
Experiment 5

TLC OF DYES AND SELECTED ANALGESIC DRUGS

Objective:
The purpose of this laboratory experiment was to identify an unknown compound by determining their Rf values and identifying the purity of solutions.

Materials:
(a)Chemicals: Food dyes(colors:FD&C yellow #5, Blue#1, Red#3, and Red#40, unknown #2), Solution of ibuprofen, aspirin(acetylsalicylic acid), caffeine, acetanilide, acetaminophen, phenacetin(p-acetophenetidide), unknown #3, Solvent system consisting of isoamyl alcohol, ethanol, ammonium hydroxide and water. Ethyl acetate.
(b)Equipments: Silica gel coating TLC plates with and without a fluorescent indictor, two developing chambers (wide mouth bottles), visualization chamber, short wavelength ultra violet lamp.

Method:
Separation of the dyes:
(1)Select a silica gel plate without fluorescent indicator.
(2)Mark a line 1cm from the bottom of the plate and across the plate draw a horizontally line.
(3)Using a pencil, gently mark four dots in equal distance and label the areas where the dyes will be applied 1,2,3,4.
(4)Spot solutions (red, yellow, blue and unknown #2 mixture on each spot separation.
(5)Allow a few minutes to evaporate the solvent of the applied solutions.
(6)In a wide mouth glass chamber with 10mL of the solvent, place the TLC plate inside and cover it, making sure that the plate is touching the glass only.
(7)Allow solvent to impregnate and ascend the plate.
(8)Let stand for about 25-30 minutes and do not move or pick up chamber.
(9)In the meantime, prepare plates for second part of experiment.
(10)Once the solvent front is approximately 0.5-1cm from the top of the late, remove it from the chamber.
(11)Quickly outline the solvent front.
(12)Place the plate inside the ventilated hood and let it dry.
(13)Measure distances on dried plate and calculate the Rf value.
Rf= distance traveled by the compound/distance traveled by the solvent front.

TLC of selected analgesic drugs
(1)Select a silica gel plate with fluorescent indicator.
(2)Follow the same procedure for the application of the dyes.
(3)Label plates with 1-7 and apply the solutions except salicylamide was not available.
(4)For caffeine add some ethyl acetate with pure caffeine from previous lab to make solution.
(5)In a wide mouth glass chamber with 10mL of solvent, place the TLC plate inside and cover.
(6)Let stand for about 20-25 minutes.
(7)Outline the solvent front and place to dry in the ventilated hood.
(8)Visualize the analgesic drugs by using the short wavelength ultra violet light to see the spots that corresponded to compounds.
(9)Gently outline spots with a pencil.

Results/Data:
TLC of dyes
Distance travelled by solvent front: 6.5cm
DYE SPOTS OBSERVED COLOR/DISTANCE Rf
Blue 4.4cm 4.4/6.5=0.68
Red 4.1cm 4.1/6.5=0.63
Yellow 1.5cm 1.5/6.5=0.23
Unknown#2 Mixed of Blue and Red —————-

Part 2
TLC of selected analgesic drugs

Distance traveled by solvent front: 4.7cm

DYE SPOTS OBSERVED(DISTANCE) Rf
Ibuprofen 4.5cm 4.5/4.7=0.96
Aspirin 0.6cm 0.6/4.7=0.13
Caffeine 1.4cm 1.4/4.7=0.30
Acetaminophen 3.6cm 3.6/4.7=0.77
Phenacetin 3.6cm 3.6/4.7=0.77
Unknown#3 1.4cm 1.4/4.7=0.30

Discussion:
Chromatography is a useful method in determining the components of various drugs because it?s a simple comparison tool to figure out unknowns from know compound Rf values. (Libretexts,2019). The first section of the lab included red, blue, yellow and unknown#2. We ran the procedure, and the solution traveled 6.5cm along the solvent front. Blue went 4.4cm, red went 4.1cm, and yellow went 1.5cm.We calculated the Rf and found that blue had a value of 0.68, red had a value of 0.63, yellow had a value of 0.23, and unknown#2 had an observed combination of red and blue.
There were a few solutions in the second part of the lab. The solution moved 4.7cm along the solvent front. Ibuprofen travelled 4.5cm, aspirin 0.6cm, caffeine 1.4cm, acetanilide 3.9cm, acetaminophen 3.6cm, phenacetin 3.6cm, and unknown#3 1.4cm. Ibuprofen 0.96, aspirin 0.13, caffeine 0.30, acetanilide 0.83, acetaminophen 0.77, phenacetin 0.77, and unknown#3 0.30 were the Rf values. The Rf values for caffeine was similar when comparing the unknown#3, indicating that the unknown was caffeine. According to the Rf data, a compound with a high Rf value is less polar because it does not stick to the stationary phase as long as a polar compound with a low Rf value. Looking at that point, we can see that ibuprofen has the highest Rf value and aspirin has the lowest, implying that aspirin is more polar than ibuprofen.

Conclusion:
The polarity or non polarity of a sample affects how it travels and interacts with molecules around it. When considering how substances travel and how quickly they move in a solvent, the extent of polarity is a huge factor that must be considered. Organic compounds and absorbents interact in a variety of ways. A weak non polar compound could only have van der Waals forces for permeability. In a less polar compound, more forces, such as hydrogen bonds or dipole-dipole forces may occur. Most importantly, in chromatography, more polar compounds are strongly permeable on absorbents, whereas non-polar compounds are weak and have a weakly absorbent. There could have been errors that caused the Rf values to be off, such as placing too many or too few sample spots on the TLC plate, or damaging the silica on the TLC plate with the pencil. This experiment demonstrated an efficient method for identifying compounds by determining their Rf values and the purity of solutions after they were placed on a TLC plate.

Reference:
Thin Layer Chromatography (2019, December 5). https://chem.libretexts.org/@go/page/2047.

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