HydroCarbon
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Salting out Caffeine
Say I have an aqueous solution of caffeine and a bunch of other junk from plant extraction. Would it be possible to cause the caffeine to precipitate
by adding a very polar solute to the solution?
Furthermore, say I had the aqueous solution with a dichloromethane layer on top of it. Would the caffeine travel to the DCM layer upon addition of a
highly polar salt?
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Nicodem
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| Quote: | Originally posted by HydroCarbon
Say I have an aqueous solution of caffeine and a bunch of other junk from plant extraction. Would it be possible to cause the caffeine to precipitate
by adding a very polar solute to the solution? |
Not likely. Organic substances generally do not like to crystallize in such media if impure with all kind of junk. You might get some precipitate but
it will be anything but pure whatever.
| Quote: | | Furthermore, say I had the aqueous solution with a dichloromethane layer on top of it. Would the caffeine travel to the DCM layer upon addition of a
highly polar salt? |
The logP of caffeine is -0.07 which means it is roughly similarly partitioned between water and moderately polar solvents like ethyl acetate,
chloroform, CH2Cl2, etc. Saturating with NaCl should help a lot, however I advise you to extract at least 3 times nevertheless. You will have to
recrystallize the extract to obtain caffeine.
There are many examples of caffeine extraction from tea leaves in student practice workbooks (some are available online) since this is a common
practice in schools. I advise you to read some.
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chemrox
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google result
I googled "caffeine experiment" and obtained the following school writeup.
Attachment: caffeine experiment.pdf (2.2MB)
This file has been downloaded 1494 times
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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HydroCarbon
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Thanks for the responses. I think I'm going to work with the extraction today. I'm going to use unroasted coffee beans as my source. Hopefully they
won't have too much other junk in them that's hard to remove.
I'll post results later.
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Nicodem
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Coffee beans, even if unroasted, are the worst source for caffeine. It contains at least twice less caffeine than tea leaves and much more other
lipid-like crap that interferes with the extraction. Before you will manage to purify the already low content of caffeine from the junk in coffee
beans, you will lose most of it. Rather use green tea (or black tea, if you don't have any green).
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HydroCarbon
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Good advice, thanks. Tea definitely does sound like a better alternative. Why do you suggest green over black though? Everything I read states
black has a higher caffeine content.
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Nicodem
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I don't think there is much difference in caffeine content based just on the green/black distinction. It much more depends on the tea brand, after all
black tea is made from green tea. I only said to use green tea because I thought it contains less compounds that might interfere with the isolation
(black tea is kind of "fermented"), but then again I'm not even sure about it.
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densest
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A quick clarification: black (also called red by Chinese speakers) tea is produced from green tea by bruising and warming the tea leaves to release
plant enzymes which oxidize various (pushing details under a rug here) components of the tea. The process changes the flavor profile quite
dramatically, but I believe it does not affect the caffeine content. Note that the three xanthines (caffeine, theophylline, and theobromine) are often
lumped together as "caffeine". They have somewhat different effects on humans, with the ratio of stimulant, bronchial dilation, and polyuria different
for each. Coffee has more caffeine than tea which has more than cacao. Tea has more theophylline than either, and cacao has more theobromine. I
haven't seen a protocol for separating the three but there must be one somewhere. It's probable that the student exercises isolating "caffeine" from
tea actually crystallize the theophylline.
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densest
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One more detail about tea - the tips of the young leaves have the highest alkaloid content. Unfortunately for the experimenter, that's the best
tasting part of the plant and thereby the most expensive. Using an excess of junk tea (Lip***, Red R***, Sala** - I can't bear to write the names in
full - it's inviting the worst from the Tea Gods) will work as well.
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Nicodem
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| Quote: | Originally posted by densest
Coffee has more caffeine than tea which has more than cacao. Tea has more theophylline than either, and cacao has more theobromine.
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Not at al! It is well known that coffee beans contain at least two times less caffeine than any tea by weight. Only the ratio between the xanthines is
different, but caffeine is the major one in both species (but not in cacao). The Coffea arabica beans rarely exceeds 1.2% in caffeine content, while
for tea it is normal to contain even more than 3%.
| Quote: | Camellia sinensis (L.) KUNTZE -- Tea; 3,810 - 93,000 ppm in Leaf;
Paullinia cupana KUNTH ex H.B.K. -- Guarana; 25,000 - 76,000 ppm in Seed;
Camellia sinensis (L.) KUNTZE -- Tea; 38,100 - 47,900 ppm in Shoot;
Coffea arabica L. -- Coffee; 600 - 32,000 ppm in Seed;
Paullinia yoko SCHULTES & KILLIP -- Yoko; 27,300 ppm in Bark;
Cola acuminata (P. BEAUV.) SCHOTT & ENDL. -- Abata Cola; 10,000 - 25,000 ppm in Seed;
Genipa americana L. -- Genipap, Jagua; 22,500 ppm in Seed GMJ;
Ilex paraguariensis ST. HIL. -- Mate, Paraguay Tea, South American Holly; 2,000 - 20,000 ppm in Leaf;
Theobroma cacao L. -- Cacao; 500 - 12,900 ppm in Seed GMJ WOI; 130 - 723 ppm in Testa JAF39:1941; 51 - 525 ppm in Petiole JAF39:1941;
Theobroma bicolor HBK. -- Nicaraguan Cacao, Pataste; 192 - 235 ppm in Testa JAF39:1941; 158 - 184 ppm in Fruit JAF39:1941; 110 - 147 ppm in Seed
JAF39:1941; 72 - 138 ppm in Petiole JAF39:1941;
Theobroma angustifolium -- Castarica, Emerald Cacao; 80 - 82 ppm in Petiole JAF39:1941;
Citrus sinensis (L.) OSBECK -- Orange; 62 ppm in Flower;
Theobroma angustifolium -- Castarica, Emerald Cacao; 35 - 57 ppm in Seed JAF39:1941; 38 - 52 ppm in Testa JAF39:1941;
Citrus limon (L.) BURMAN f. -- Lemon; 50 ppm in Flower;
Citrus paradisi MacFAD. -- Grapefruit; 29 ppm in Flower;
Citrus sinensis (L.) OSBECK -- Orange; 6 ppm in Leaf; 0.3 ppm in Bud;
Annona cherimola MILL. -- Cherimoya; in Seed;
Firmiana simplex (L.) W. F. WIGHT -- Chinese Parasol; in Seed;
Guazuma ulmifolia LAM. -- Bay Cedar; in Leaf;
Paullinia yoko SCHULTES & KILLIP -- Yoko; in Leaf; |
Cited from "Dr. Duke's Phytochemical and Ethnobotanical Databases", a search results for caffeine.
| Quote: | | I haven't seen a protocol for separating the three but there must be one somewhere. It's probable that the student exercises isolating "caffeine" from
tea actually crystallize the theophylline. |
No, those students indeed separate the major xanthine which is caffeine. A single recrystallization should be enough to purify caffeine from other
xanthines and contaminants.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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densest
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Thanks for the clarification - I'll back-pedal and agree that what I meant to say was the ratios Coffee/Tea/Cacao were different. I'm surprised at the
reference saying tea has more caffeine than theophylline - I'll have to go back and recheck my sources.
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Nicodem
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As far as I know cocoa (Theobroma cacao seeds) is the only plant product that contains large amounts of theophylline (often it contains only
two times less theophylline than theobromine which in pure crude cocoa can amount up to 3%!). Tea leaves only contain traces of it, caffeine being the
major alkaloid leaving others a long way behind.
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pantone159
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Would it be practical to try and separate the theobromine from cacao? Would something like the procedure for extracting caffeine from tea work there?
At least for extracting the mixture of the alkaloids.
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HydroCarbon
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| Quote: | Originally posted by pantone159
Would it be practical to try and separate the theobromine from cacao? Would something like the procedure for extracting caffeine from tea work there?
At least for extracting the mixture of the alkaloids. |
It should work just like a caffeine extraction. Just by looking at the structure theobromine should be even more basic than caffeine due to the NH
group in the cyclohexene ring. This will allow it to be protonated easier.
I played around with some caffeine the other day, testing solubility and other stuff. Here's what I came up with. Most of it is obvious, but I just
wanted to prove it.
Solubility
Methylene Chloride: High
dH2O: Negligible
1M HCl Solution: High
1M NaOH Solution: Negligible
Hexane: Negligable
Addition of hexane to methylene chloride caffeine solution causes precipitation.
Addition of 6M NaOH to 4M HCl caffeine solution causes precipitation.
Addition of 1M NaOH to 1M HCl caffeine solution did not cause precipitation.
I also attempted an extraction. I made a 0.56% (w/w) acidic (HCl) caffeine solution, baseified with a 0.014 molar excess of NaOH, and successfully
extracted from the aqueous layer with methylene chloride. I didn't check my yield, just that it was there; but it must have been there in appreciable
quantity since the resulting solution left a nice strong TLC spot similar to that of the original solution.
I'll probably attempt the tea extraction sometime next week. I'll be sure to test for theophylline in the resulting product.
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sparkgap
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| Quote: | Originally posted by HydroCarbon
It should work just like a caffeine extraction. Just by looking at the structure theobromine should be even more basic than caffeine due to the NH
group in the cyclohexene ring. This will allow it to be protonated easier.
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Two (minor) points of contention:
1. There is no cyclohexene ring in the structure of theobromine, or caffeine for that matter; only the purine ring system.
2. As to separation, I invite you to look at the handy pKa table at this link (and you can get the whole book here).
sparky (~_~)
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HydroCarbon
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Right, somehow I missed those big N's in the structural diagram  .
Thanks for the link to the book, it should help me greatly.
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mewrox99
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Extraction of caffeine in coffee
Is there any easy way to extract caffeine from solid coffee powder. This will be my first organic extraction.
I'll be doing this in a school lab so I should have a ok range of solvents (DCM, propanone, ethanol, hexane etc.)
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Lambda-Eyde
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Google holds your answers. This is one of the first results from "extraction of caffeine": http://www.seriaz.org/downloads/4-caffiene.pdf
I see that you're new here; welcome! For your information, these types of topics belong in the beginnings section.
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Nicodem
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Threads Merged
14-6-2010 at 04:25 |
Nicodem
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Merged the last two posts in the already ongoing caffeine extraction thread...
See also http://www.sciencemadness.org/talk/viewthread.php?tid=12270
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rrkss
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Just want to add my 2 cents. Be very careful when you shake the seperatory funnel while doing the extraction. The organic acids seem to act like
detergents when you basify them prior to doing the extraction and form a nasty emulsion if you agitate the sep funnel too much. Been there and this
emulsion is very difficult to break.
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The WiZard is In
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Quote: Originally posted by HydroCarbon  | | Say I have an aqueous solution of caffeine and a bunch of other junk from plant extraction. Would it be possible to cause the caffeine to precipitate
by adding a very polar solute to the solution? |
------
Up to the 70's trichlorethylene was used to decaffeinate coffee.
[It was also used as an anesthetic during child birth.]
5-10 years ago you could buy it OTC, it was a common industrial
chemical and had replaced carbon tetrachloride for household
use. It was replaced by 1,1,1 tetrachlorethylene, which was
replaced by .......?
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peach
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I ran a quick extraction on Coffee for something to keep me busy. There's a thread here with a ton of photos for you to have a browse over.
CLICK ME
I would make a few recommendations to improve on that method. Split the DCM into two parts and do two separate extractions on the aqueous phase. If
you recrystallize, keep the filtrate and do it again to see if you can squeeze some more out.
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Random
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Do I have to use DCM or I can also use acetone or butanone (MEK)? Can chloroform be used?
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rrkss
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I'd use something insoluble in water. Caffeine is very soluble in chloroform and can be used as a substitute for DCM.
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