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LAB 5-COLUMN CHROMATOGRAPHY OVERVIEW:
(Full text)
1. Preparation of the sample:
Take a known amount of the mixture of ferrocene and acetoferrocene and dissolve it in methylene chloride. Spot this on a TLC plate. Add alumina to the solution and let it dry.
2. Preparation of the column:
a. Obtain all three solvents needed for elution.
b. Place a small wad of glass wool at the bottom of the column.
c. Add hexane to the column and then add basic alumina onto it.
d. Drain the solvent until its level is about a cm above alumina.
e. Add sand to form a thin layer. Adjust the solvent level so that it is just above the layer of sand.
3. Loading the sample:
a. Transfer the previously prepared dried mixture of ferrocene, acetoferrocene, and alumina to the column. Add sand to form a thin layer above the sample.
b. Add small portions of hexane to allow the sample to run onto the column. Continue to do this till the solvent above the sand remains colorless.
4. Elution of the fractions:
a. Fill the column with hexane and open the stopcock.
b. Collect the initial colorless fraction in the waste beaker.
c. Start collecting the first colored fraction in beaker1, when it is about a cm from the glass wool.
d. Change the elutant to 10:1 hexane-ethyl acetate and collect this intermediate fraction in beaker 2 until the second colored band is about a cm away from the glass wool.
e. Change the elutant to 1:1 hexane-ethyl acetate and collect the second colored fraction in beaker 3 until it is completely eluted.
5. Isolation and Identification:
a. Transfer the two colored fractions to two pre-weighed RB flasks.
b. Evaporate off the solvent using rotovap and weigh the flasks.
c. Dissolve the solids in the RB flasks and spot them on the TLC plate.
d. Spot standard ferrocene and acetoferrocene on the TLC plate. Develop the plate and identify the components.
Go to Rotovap Page for instructions on how to use the rotovap apparatus.
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