In this video caffeine is extracted from tea using dichloromethane.
The crude extract is purified by recrystallization with ethanol.
I am going to add about 75 mL of water to a 200-mL beaker.
Then I am going to throw in a few boiling stones.
I am going to cover the beaker with a watch glass and turn on the temperature to get it
to boil.
Once it starts to boil, I’ll add two packets of tea.
Okay, after it’s been boiling about 5 minutes now, I am going to go ahead and take out the
packets, and I will try to get back as much of liquid as I can by squeezing it between
two watch glasses.
And I’ll grad the other one out.
I am going to remove it from the hotplate and I’m just going to cool it a little bit
in this ice.
So now I am going to add about 1 gram of sodium carbonate, which will convert the tannins
to water-soluble salts.
Okay, and now I will add the solution into a separatory funnel, and I will leave behind
the boiling chips so they do not get stuck in the funnel.
For the extraction then I will use about 10 mL of dichloromethane and I’ll extract it
three times and then combine the extracts.
This is probably the hardest part is to extract this without forming an emulsion.
So instead of vigorously shaking it, I am just going to tip it over a few times.
It looks like it worked pretty good.
I have very good separation, a little bit of bubbles in between, but nothing to bad.
So now I will just drain off the bottom layer.
So I will add another 10 mL or so.
Okay, and again, I am just going to tip it over.
Okay, I got great separation again.
If I needed to, I could potentially put the stir rod in there to break up some of the
bubbles.
I am going to drain the bottom layer off.
And I’ll extract it one last time.
Okay, you see I have some there, again there is probably a little bit more, but I’m just
going to set it aside for now.
So, the solution is a little bit cloudy.
There is a little bit of brown spots, so there is some impurities there, but for the most
part it looks okay.
So now I will add anhydrous sodium sulfate to dry the solution to remove any water that
may have come over with the dichloromethane, or come out with the dichloromethane.
Solution is already looking a lot clearer.
Okay, and I'll just let it sit for a few minutes.
Now that it sat for a few minutes in the anhydrous sodium sulfate, I'm going to transfer it to
a crystallization dish so it can evaporate the fastest.
I will just decant it and try not to get any of the sodium sulfate to come over.
I'll add this to the hotplate.
I'm also going to rinse this one time.
This is boiling pretty good, but just to help it boil a little more, I'm just going to put
in that wood stick.
I'm just going to keep an eye on it just so I don't evaporate it all and start heating
the crude caffeine directly.
Well, I can see it starting to solidify a little bit, so I'm going to remove it from
the heat.
Okay, it looks like it is almost all gone there.
So with this remaining amount I'll let it evaporate slowly, or at least without any
heat directly applied to it.
There is not a lot of it.
The color looks really good though, it is not yellow or anything, but if it is yellow
or if it does look a little cruddy, that should be taken care of when we do recrystallization.
So I'm going to try to scrape some of this up.
It doesn't seem to working very well.
Instead of trying to scratch it up, an easier way to transfer this would probably be to
dissolve it in the recrystallization solvent first.
Okay, so I'm going to add now 100% ethanol to it to dissolve it and then transfer it
to a test tube.
Alright, so I have it re-dissolved in hot ethanol and now I'm going to transfer this
to a small test tube.
Okay, you can see I do have some of it left behind, not all of it made it, but a decent
amount made it to the test tube.
Okay, now I'm just going to add it an ice-water bath to minimize the solubility and hopefully
purified caffeine will crash out of it.
After it has been sitting in the ice for about 5 minutes, I'm going to collect it using the
Buchner funnel.
I also have some cold ethanol to help with the rinse.
Unfortunately, the vacuum is not working right now in the building, so I got a modified vacuum
here where I'm going to use this syringe and I'm going to pull it up to create a vacuum
to suck the solvent through.
Okay, so I'm first going to take the ice-cold ethanol and wet the filter paper.
Works a little bit anyway, works good enough I guess.
Okay, I'll try to collect the crystals as best I can.
I got quite a bit that never made it out of the flask.
I guess I'll add some ethanol to it.
Looks like I most of them out of the test tube.
Now I'm just going to transfer it to a little vial.
And there we have it.
Some recrystallized caffeine from ethanol, formed some really nice needles.