Science Buddies: "Ask an Expert"

How can I measure the amount of caffeine in different liquids? Will I be able to do this at home or do I need fancy equipment?
(My experiment question is, what is the best way to decaffeinate tea at home?)

Hi lkjhgfdsa,
I am sorry to say that there doesn't appear to be any commercially available test kit for testing caffeine level for home use.
However, several universities are researching this technology. You may want to see if there's some way that you could incorporate your research with theirs.
Here's an URL / recent news stories on the subject for your review:
http://phys.org/news/2013-08-caffeine-traffic.html

Good Luck with your experiment and please let us know if we can be of any additional help!
Willey

So do you think that I will be able to do this project? How can I determine which liquids have more caffeine if I can't measure it?

Hi lkjhgfdsa,
Yes, you may still be able to do this project. If you can't measure the amount of caffeine directly, you may be able to measure the effect of the caffeine instead.

For example, in this case with the tea and decaffeinated tea, you may be able to get a few volunteer to drink the tea and then measure the effect it has on their heart rate. The trickiest part is that you will need to formulate a really detailed procedure so that you can be certain that the only thing affecting their heart rate is the tea. (So, you will want them to be in the same room, the temperature of the tea should be about the same, and you will need some type of control such as water, etc...)

Good Luck and please let us know how it goes!
Willey

Thank you so much!

I found out that tannic acid is supposed to form white precipitate when it comes in contact with caffeine, but I am not sure if this is true, as I only saw this method come up in one science experiment. I also researched more about it onine, but I did not find out much about. I think that it this is true, then this would be a good way to determine which liquids have more caffeine in them. Here is where I found out about tannic acid (Link:http://maggiesciencefairproject.weebly. ... usion.html) Do you think this method might work for me or not? Thank you.

Hi lkjhgfdsa,

Like you, I found a few references about a precipitate forming from tannic acid and caffeine. One of those was in a chemistry book published in 1879!

I think that you might be able to use this idea to detect the presence of caffeine. This may require some experimentation to get a workable procedure. Evidently the one described in the link you provided did not work, but you might use that procedure as a starting point.

The precipitate test may not be useful for finding the amount of caffeine in your teas. Precipitates can be used to find amounts of chemicals present. But this is applicable for complete reactions where all of the chemical in question precipitates. The precipitate is collected and quantified in some way (weighed for example). I think that the tannic acid reaction may not be complete so this will not work for finding the amount of caffeine.

Another idea came to mind after reading all of the posts on your topic. You might consider finding the amount of material extracted from your tea leaves as a result of different decaffeination trials. To do this you could weigh the tea leaves, decaffeinate, then dry the leaves and re-weigh. The weight difference divided by the original weight would represent the percentage of material extracted by the decaffeination trial. With this kind of experiment you could compare the amounts extracted by different home decaffeination methods.

I hope this helps and good luck! Please ask again if you have more questions.

A. Norman

However, I want to measure the caffeine in the actual tea (the liquid). Is it possible to isolate caffeine by letting the water in the different teas evaporate? Or could I just have someone drink each of the different teas and measure the heartbeat (I heard that consuming more caffeine usually leads to a faster heartbeat), and decide which tea had the most caffeine that way? Thank you so much for your help.