HEEELLLPP Caffeine

[rachydean]

can anyone help me!!

i chose to do chemisrty ofr my exyended essay and have done the extraction of caffeine from tea bags however i have got to a point no where i only used 6g of tes but have like 5g of white-ish powder. the method i used said to add Sodium Sulfate (Na[sub][/sub]2SO[sub][/sub]4) i guess the powder is a mixture of the caffeine and the sodium sulfate but how do i get the caffeine from that. the method i have been following all the way through says to do a sublimination but im not sure any tips would be loved!

[silverks]

[quote name='rachydean' post='19555' date='Jul 9 2008, 09:32 PM']can anyone help me!!

i chose to do chemisrty ofr my exyended essay and have done the extraction of caffeine from tea bags however i have got to a point no where i only used 6g of tes but have like 5g of white-ish powder. the method i used said to add Sodium Sulfate (Na[sub][/sub]2SO[sub][/sub]4) i guess the powder is a mixture of the caffeine and the sodium sulfate but how do i get the caffeine from that. the method i have been following all the way through says to do a sublimination but im not sure any tips would be loved![/quote]

Ok, 5g of that white powder obtained from 6g of tea leaves is definitely NOT caffeine. In all probability the amount of caffeine you should get is in the scale of milligrams. For 6g of tea leaves, you should be able to get around 30 to 60 milligrams of crude caffeine.

If that white-ish powder is indeed the sodium sulphate, then sublimation is required to separate them. Caffeine is known to undergo sublimation at around 178 C while anhydrous sodium sulphate will melt at extremely high temperature (844 C), so you should be able to easily separate them by sublimation technique.

However, you should not have gotten that much white-ish powder in the first place. I've done caffeine extraction multiple times before and managed to extract crude caffeine (what you call the white-ish powder) from 0.004g to 0.020g, depending on the brand and type of tea leaves used.

If you could list out your extraction methods I may be able to help you out further.

[booji]

[quote name='silverks' post='20478' date='Jul 24 2008, 10:34 AM']Ok, 5g of that white powder obtained from 6g of tea leaves is definitely NOT caffeine. In all probability the amount of caffeine you should get is in the scale of milligrams. For 6g of tea leaves, you should be able to get around 30 to 60 milligrams of crude caffeine.

If that white-ish powder is indeed the sodium sulphate, then sublimation is required to separate them. Caffeine is known to undergo sublimation at around 178 C while anhydrous sodium sulphate will melt at extremely high temperature (844 C), so you should be able to easily separate them by sublimation technique.

However, you should not have gotten that much white-ish powder in the first place. I've done caffeine extraction multiple times before and managed to extract crude caffeine (what you call the white-ish powder) from 0.004g to 0.020g, depending on the brand and type of tea leaves used.

If you could list out your extraction methods I may be able to help you out further.[/quote]

First of all, if you have access to an IR, UV-Vis, or NMR spec, get a spectra of the white powder that you have extracted. If indeed caffeine is present you should see a characteristic pi --> pi* transition in the UV-Vis spectrum, and similarly you should see characterisitc C-C stretch in the IR spectrum. This will confirm if you have indeed extracted caffeine. After that, you could try extraction of that solid with various organic polar solvents (acetonitrile comes to mind). Your best bet would be to consult the literature to see which organic solvent would work best. I am sure there are a plethora of articles on SciFinder of CSA, etc.

[silverks]

[quote name='booji' post='21178' date='Aug 1 2008, 03:12 AM']First of all, if you have access to an IR, UV-Vis, or NMR spec, get a spectra of the white powder that you have extracted. If indeed caffeine is present you should see a characteristic pi --> pi* transition in the UV-Vis spectrum, and similarly you should see characterisitc C-C stretch in the IR spectrum. This will confirm if you have indeed extracted caffeine. After that, you could try extraction of that solid with various organic polar solvents (acetonitrile comes to mind). Your best bet would be to consult the literature to see which organic solvent would work best. I am sure there are a plethora of articles on SciFinder of CSA, etc.[/quote]

Even if you don't have those advanced analytical equipment like IR, UV-Vis, or NMR spec, you can use thin layer chromatography (TLC) technique to verify that it's caffeine. For this technique, you should compare the sample you obtained with a sample of pure caffeine (your school can obtain it from chem substances supplier). This technique will also tell you whether the caffeine you extracted is pure or contains impurities (the latter is more likely).

About the solvent, I used dichloromethane before and it worked fine. But practise goob lab habits, though. Dichloromethane, like most other organic sovlent, is a suspected carcinogen. Always wear glove when handling them and do your extraction in a gas hood.

[babakren]

I agree with booji, my friend tried to do a caffeine determination but he decided not to do it because the caffeine is hard to trap. But to extract the caffeine you could use a perforator and use chloroform to extract it. I'm not really sure with the details but i could only suggest that you should extract it in a closed system where you can trap all the gas.