[knos1kus]

Hello, chemists!
Im 17, right now Im working on schools research. My goal is to compare caffeine % in different sorts of teas, coffees, other beverages etc. I have already done some information research, I have written theory part about caffeine influence, synthesis. But I still havent found any more or less possible way how to find exact %. I have seen some qualitative reactions, and even some quantitative, but most of them are impossible to make in my school lab. Most possible way, that i have found is some sort of Iodometry, but I havent really understood is it possible to use it for teas, coffee etc. So, my question is, is it possible? and could some of you, please, leave some good link or book where I can find exact instruction of doing this.
Looking forward for your answer.
P.S. Sorry for my bad English.

[Raayou]

Search in Google AOAC Methods of Caffeine determination in food, soda and brevages.  The principal  method  involved is liquid Chromatography. .  Or message me for more details.

[Corribus]

High school student probably doesn't have access to an LC/MS. When I did this in high school, I did a simple extraction using methylene chloride or ethyl acetate and then mass analysis of the dried residue.