CHML211
Exp. 7 Recrystallization, Melting Point and HPLC of Analgesics
IN-LAB ASSIGNMENT: (EACH STUDENT will record the following data in his/her laboratory notebook in a well organized
manner during lab period. Yellow carbon copies will be submitted for grading along with Post-Lab assignment.) …..max
score = 20 pts.
6. Data/Calculations (The following information should be recorded directly into laboratory notebook.)
a.
b.
ASPIRIN
i. Weight of large filter paper + small filter paper + aspirin (from extraction)
ii. Actual weight of aspirin (from extraction)
iii. Weight of small filter paper
iv. Weight of large filter paper (for storage)
v. Experimental melting point of EXTRACTED aspirin
vi. Experimental melting point of IMPURE aspirin
vii. Experimental melting point of RECRYSTALLIZED aspirin
viii. % recovery calculation
ix. HPLC vial slot #
ACETAMINOPHEN
i. Initial weight of acetaminophen (from extraction)
ii. Weight of large filter paper (for storage)
iii. % recovery calculation
iv. Experimental melting point of RECRYSTALLIZED acetaminophen
v. HPLC vial slot #
7. In-lab Questions (The following questions should be answered in laboratory notebook.)
a.
The UV detector on the HPLC instrument detects compounds that absorb UV light in the range of 254 nm.
Compounds containing multiple bonds and aromatic rings can typically be detected at this wavelength.
Which of the following compounds would you expect to be detected and appear in the HPLC chromatogram
of your sample?
O
O
H
N
O
O
OH
OH
O
H
H
O
O
OH
b.
In some instances, a sample will appear to be pure based on HPLC analysis; however the experimental
melting point will be lower than expected. Give one possible source of this inconsistency and explain why it
occurs.
CHML211
Exp. 7 Recrystallization, Melting Point and HPLC of Analgesics
POST-LAB ASSIGNMENT: (EACH LAB GROUP will submit one copy of a typewritten, paragraph style report addressing
all of the points listed below. Must be written using PAST TENSE, PASSIVE VOICE. ) …..max score = 50 pts.
8. Experimental (Write 1-2 paragraphs including all of the following. Do NOT present a bulleted outline.)

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Describe the process used to purify the aspirin by recrystallization. Include names, mass/volumes of any
compounds used during this purification process.
Describe how the HPLC sample was prepared. Include how much sample, the identity/volume of HPLC solvent
used, and give the vial slot number.
Describe how the aspirin sample was prepared for storage, including masses of any filters or glassware used for
this step.
Describe the process used to purify the acetaminophen by recrystallization. Include names, mass/volumes of any
compounds used during this purification process.
Describe how the HPLC sample was prepared. Include how much sample, the identity/volume of HPLC solvent
used, and give the vial slot number.
Describe how the acetaminophen sample was prepared for storage, including masses of any filters or glassware
used for this step.
Describe the process of obtaining the experimental melting point and calculating percent recovery for each
compound.
9. Results (Copy and paste the completed tables into your document.)
Table 7.1 Experimental results
Aspirin
Acetaminophen
* Theoretical recovery after extraction (g)
*Actual recovery after extraction (g)
*Percent recovery after extraction
Theoretical recovery after recrystallization (g)
Actual recovery after recrystallization (g)
Percent recovery after recrystallization
* From Table 6.1
Table 7.2 Melting point results
Impure aspirin preparation (oC)
Extraction sample melting range (oC)
Recrystallized sample melting range (oC)
Literature melting point value (oC)
Sample
Compound
Aspirin
Acetaminophen
-----
139–140
169–172
Table 7.3 Recrystallization HPLC results
HPLC retention times (min) and area %
Aspirin
Acetaminophen
Standard
Sample
Sample
Rt
Rt
area %
Rt
area %
(min)
(min)
(min)
Aspirin
Acetaminophen
10. Discussion (Write 1-2 paragraphs including the following.)


What was the percent recovery of the aspirin after the extraction technique? What was the percent recovery of
aspirin after the recrystallization technique? If more than 20% of the aspirin was lost during the purification
process, propose a possible source of product loss.
What was the experimental melting point of the extracted aspirin sample? What was the experimental melting
point of the recrystallized aspirin sample? Compare these values to the literature melting point for aspirin. Did
the recrystallization technique result in any purification of the aspirin sample? Give a final comment on purity of
the recrystallized aspirin.
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What was the percent recovery of the acetaminophen after the extraction technique? What was the percent
recovery of acetaminophen after the recrystallization technique? If more than 20% of the acetaminophen was
lost during the purification process, propose a possible source of product loss.
What was the experimental melting point of the recrystallized acetaminophen sample? Compare this value to the
literature melting point for acetaminophen. Did the recrystallization technique result in any purification of the
acetaminophen sample? Give a final comment on purity of the recrystallized acetaminophen.
Based on HPLC analysis of the aspirin sample, is there any indication of acetaminophen present? Give the name
and area % value(s) of any compound in this sample chromatogram. Based on HPLC analysis of the
acetaminophen sample, is there any indication of aspirin present? Give the name and area % value(s) of any
compound in this sample chromatogram.
Based on the statement above, was pure aspirin isolated? And pure acetaminophen? Briefly explain.
Include a short comment addressing what could be done differently to improve the experimental results, if
repeated.
Be sure to attach your HPLC sample chromatograms to your final lab report!