Romain - 10-3-2015 at 08:32
Hi everybody,
I recently extracted, using dichloromethane, 820 mg of what looks like reasonably pure caffeine from 100 g of instant coffee. The caffeine was
recrystallized once with acetone and now looks like a yellow-white fluffy crystalline powder. This represents a yield of around 26 %. (According to
caffeineinformer.com, 1.8 g of instant coffee contains 57 mg of caffeine) I have yet to test the purity of the product by measuring it's melting
point.
While 820 mg is not too bad, I want to extract more caffeine - around 10 g if possible - to try to obtain nice crystals from it. So I bought some
caffeine food supplement for sport. The bottle contains 150 pills of 610 mg each but they are not pure caffeine. The bottle says 100 g of pills
(including the gelatine capsule) contains:
14 g Saturated fatty acids
41 g Dietary fibre
19.7 g Protein
24.6 g Caffeine
That amounts to 99.3 g so the other contaminants are negligible.
And it also lists the ingredients as: Fillers (microcrystalline cellulose), Caffeine, Gelatine, Separating agents (Magnesium stearate), Colourings
(TiO2, Iron oxide, Azorubine).
The goal here is to get separate the caffeine from the rest.
I weighed the following
The pill (capsule + contents): 0.64 g.
The contents (powder): 0.51 g.
The capsule: 0.12g
My scale is not the best in the world as you can see... Anyways, I know that capsules are usually made of gelatin (protein) and here the capsule
represents 19 % of the weigh, so this means that by just emptying every capsule an collecting the contents, we can get rid of the protein part very
easily.
Now we are left with fatty acids, microcrystalline cellulose and negligible contaminants and that's where I need your help. I think I could get rid of
the cellulose by simply dissolving the caffeine in DCM, acetone, EtOH, EtAc, but the fatty acids might also dissolve in these solvents.
I don't know which fatty acids there are, but they are saturated. I guess a non-polar solvent like white spirit could word but I would like your input
on the subject.
Sorry for this long post, if you don't have time to read it all, basically how does on separate Caffeine, Cellulose and Saturated fatty acids?
Thanks in advance for your help!
P.S. I don't have access to pure caffeine powder and it's much more fun and rewarding to extract it myself anyway.
mayko - 10-3-2015 at 09:02
When I was in school, we extracted caffeine and then used purification by sublimation.
Romain - 10-3-2015 at 09:16
Unfortunately I don't have access to a vacuum pump so I can't use sublimation to extract the caffeine.
Dr.Bob - 10-3-2015 at 09:20
If you dissolve the contents in boiling water, the caffeine will come over, but the fats may ppt or separate once the water cools. Then you could
extract with DCM or EtOAc. But the fatty acids will stay in the organic as well, you might be able to keep them in the water by keeping it basic, but
that will form soap, which may make the extractions a mess. Sublimation might work, but if you can minimize the fats, that will make it work better.
Also a recrystallization from hot water or ethanol might be able to get rid of the fatty acids.
Romain - 10-3-2015 at 11:47
I looked up stearic acid on Wikipedia because it was the first solid saturated fatty acid I could think of. It turns out that it is used in dietary
supplements so it may be in the pills I have too. Just conjecture though.
Anyway, as you said Dr.Bob, the fatty acid may precipitate upon cooling of the water. Stearic acid for example is 3000 more soluble at 37 °C than it
is at 20 °C (0.003 g/l at 20 °C vs 9.93 g/l at 37°C). I'll have to test that.
I just tried dissolving the powder inside one of these pills. I stirred it in hot water for about 10 minutes. The cellulose, and possible the fatty
acid are extremely insoluble and hydrophobic; they stayed completely wet on top of the solution. I then filtered the solution and it is now
evaporating.
Almost all of the caffeine of the pill (150 mg according to the box) should have dissolved in the excess of water.
What I'll have to check is the presence of fatty acid in the caffeine I obtain after evaporation.
If that is the case, could white spirit dissolve the fatty acid and not the caffeine?