Determining the Rf values for a Series of Compound Mixtures using Devolvement Solvents.
a. Take a TLC plate
b. Draw a line 5mm from the bottom using a pencil
c. “Spot” each compound in a separate lane.
d. Develop the plate with 80:20 hexane:ethyl acetate
e. When solvent is close to top of TLC plate, remove it from chamber and mark that stop point
f. Leave plate to dry
g. Use UV lamp to localize the spots and circle each with a pencil
h. Calculate Rf for each compound
i. Repeat using 100% hexane and 60:40 hexane:ethyl acetate
j. Discuss effects of different solvents and establish polarity order
Part 2: Analyzing Known Analgesics
a. Use ethyl acetate:CH2CL2 (1:1, most polar) and ethyl acetate:hexane (10:1)
b. Calculate the Rf values of aspirin, acetaminophen, and caffeine to determine their polarity order (observe which is more polar)
c. On the same plate, run a reference sample with all 3 solutes mixed together (observe visibility)
d. Use the UV lamp and circle each mark
e. Determine the order of polarity and think if order makes sense.
Part 3: Analyzing commercially available analgesics using solvent pairs (from part 2)
a. Evaluate the unknown commercial analgesics and determine identity –
b. Compare Rf values of the individual compounds to the TLC of the unknows
