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Guest Zeus

Caffeine extraction from coffe or tea

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Guest Zeus

Hi all, does anyone know how to extract pure caffeine from coffee beans or tea? I need a proven method.

Thanks.

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i think this is a pretty common chem prac, you should get plenty of search hits with google.com

i remember finding a few pages a couple years ago with photos, etc

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Originally posted by Zeus:

Hi all, does anyone know how to extract pure caffeine from coffee beans or tea? I need a proven method.

Thanks.

How pure do you want it to be, and how much trouble are you willing to go to? I mean, No Doze are just sitting there for the asking. The quick and dirty method is to make a pot of strong tea or coffee (duh!), strain, and then condense the liquid down to a powder (or, more likely, a goop). You will have brown tannin and other stuff in there as well as the caffeine, but it's at least a starting point.

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If you want all the alkaloids then methylene chloride works good (its pretty much the 'standard extraction procedure' in the colleges) but the product will contain other alkaloids and a little funky crap (impurities). It requires multiple extractions though because caffeine freebase is soluble in water. However if you want a product thats mostly caffeine then dont use tea, it contains hella theobromine, theophylline, and a few others. If you insist on using tea then use black tea, it'll give the highest yield by far. I would not suggest using it for drug purposes though, it is very easy to unknowingly consume a toxic dose and in the pure state the caffeine from three cups of coffee, consumed on an empty stomach, can be bad for you so take with food and drink if you insist on taking it at all [When I was like 11 or 12 I got caffeine pills, extracted with water, filtered, concentrated, and recrystalized to get a moderatly pure product that damn near made my heart explode when consumed by itself, but worked (and tasted) good when sprinkled on slices of apples, especially if you cut the caffeine with vitamin C, Mmmmmm Good. If I hadn't already been a coffee drinker it probably would have sent me to the hospital!]

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Hehe... This morning I tried about 100mg of the re-crystallised alkaloids that we extracted from tea for a prac at uni this week. Was an interesting experience to feel the caffeine effect without having tea or coffee breath (or eating some no-doz tablets that you don't have any personal experience in preparing yourself).

There is a smallish yellow book simply called 'Natural Products' that has some interesting practical projects in it that people here might find interesting. I can't remember the author, but i reckon they are on the ball... wink.gif I think we used basically the same caffeine extraction procedure that's in that except we used more tea and scaled up the rest. We got some nice crystals... so it works, but you really need to extract the aqueous layer quite a few times with DCM (and make sure you mix the layers thoroughly). i don't think i did this enough and only ended up getting about 250-300mg of alkaloid from 75g of black tea (even before hot-filtration and re-crystallisation). The funny thing is, i ended up getting about the same yield when i used green yea (for which a HPLC comparative analysis said there should be only about %40 as much caffeine as the black tea). Maybe my extraction technique was better the second time round when i did the green tea. I'd be interested to try guarana and see what the yield is like. Any guarana heads out there who would like to bioassay some guarana alkaloids?

[This message has been edited by Fractalhead (edited 09 August 2002).]

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Some varieties of chocolate, called criollo, have comparable levels of caffeine as coffee.

Some green teas will have the same caffeine content as black teas, possibly a little more bound by acids in green tea so not so visible in a HPLC extract?

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Hmmm... yeah i don't know if he neutralised the acids in the samples before running them... or if the acids would even effect the results.

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"sublime it @ about 200 degrees."- bloodbob

Yup, that'll work if you use a controled oil bath to heat the sample to be sublimed. You dont want to over-heat.

Caffeine sublimes at 180 C

Theobromine sublimes at 290 C

I dont have numbers on theophylline sublimation, but my crude estimate based on melting points and structure seems to indicate that it would be closer to caffeine than theobromine:

Caffeine mp 236.8

Theophylline mp 272-4 C

Theobromine mp 351 C

So I would do sublimation (preferably in a vaccum sublimation aparatus) at 180-200 C.

Of course one must ask oneself if its worth it. Has anyone done a comparitive bioassay between the crude alkaloid mix and pure caffeine to see if it makes much of a diffrence? After all theobromine is said to act as a smooth muscle relaxant (as well as being a stimulant) so maby the mixture would be more pleasant. Stimulant-muscle relaxant sounds better than a straight stimulant to me.

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Actually you really don't need to heat it to the point of sublimination you just need to heat the caffiene sufficiently to to cause a large increase in vapour pressure so you could probably do it @ around 150 c.

Another important note is that if you have NaOH/KOH in your product its going to decompose espically if you try to heat it so try to wash out all the excess NaOH.

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"wash out all the excess NaOH"- bloodbob

You dont need it to start with. Caffeine is a very weak base, a little bit of baking soda put in the coffee would be enough to ensure a freebase and actually you probably wouldn't have to add a base at all, just extracting coffee repeatedly with methylene chloride will give you freebase caffeine.

And dont forget that the freebase IS moderatly soluble in water. Contrary to common net chatter there is no solubility rule for alkaloids in general. Some are very soluble in water, some are virtually insoluble in water, most are somewhere in between.

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