Sample results and Laboratory report
MICROSCALE ANALYTICAL EXPERIMENT
Thin Layer Chromatography Analysis and Purification of Aspirin by
Recrystallization
Sample data and results
Sketch the TLC plates from step 14 and step 29 in 1:1 scale below
Step 14
S: Impure sample
A: Aspirin
Rf values: Aspirin is 0.58
Impurity is 0.18
Step 29
Rf values: Product is 0.58
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Weight of empty vial = __7.7457g______
Weight of vial and recrystallized product = ____7.8981g______
Weight of recrystallized product = ___0.153g____
Melting point of purified aspirin = ___133 – 135 oC_____
Questions
1. Calculate the percentage recovery of your purified aspirin.
Weigh of impure sample before recrystallization = 0.2035g
Weigh of crystal after recrystallization = 0.1524g
Percentage recovery = (0.1524g / 0.2035g) x 100% = 74.9%
Note: Students got their percentage recovery ranging from 54 – 75%
2. Compare the TLC result obtain from step 14 and step 29, comment on the purity of your
recrystallized aspirin.
Compare the two TLC results, it is shown that the recrystallized aspirin is pure as no spot
corresponding to the impurity with Rf value 0.18 was found in the TLC plate given by the
recrystallized crystal. Only one spot corresponding to aspirin was seen in the TLC plate.
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3. Interpret the IR spectrum of your purified aspirin.
The IR spectrum of aspirin is shown below
O
OH
O
O
Wavenumber (cm-1)
Wavenumber
2400 – 3200 cm-1 (br)
3017 cm-1
2871 cm-1
1757, 1692 cm-1
1607, 1461 cm-1
Assignment
OH (carboxylic acid)
C–H (unsaturated)
C–H (saturated)
C=O
C=C
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