Re: Finding concentration of caffeine

Mark wrote:
A student wants to find the concentration of caffeine in coffee beans. We have a method of extraction, using ethyl acetate. Anyone know of a simple way of determining the concentration of the solution produced. We are a small school with limited apparatus so suggestions such as HPLC, Mass spec and UV spectroscopy are not an option ... although we do have things like burettes, colorimeters and a finite budget!

Thank you

Did this in high school. Found an old recipe using extraction and Kjeldahl analysis...don't remember the ref, and I'm 1000 km from home...

Apparently the main source of extractable nitrogen is caffeine. Believe I used chloroform iirc...
The evaporated extract was digested, standard Kjeldahl method. Addition of base released ammonia, which was collected in acid and back-titrated.
No use of fancy apparatus or the like.

It was crap, did not work for me. But it should in principle given decent lab prax etc.

Anecdotal: I needed a Kjeldahl analysis once while working as a chemist as an attempt to digest a particularly incombustible polymeric sample I made; called the one lab that still did it asking if they could do it...after a moment the guy at the other end asks:
Well, is it faeces or dirt?

The method has it's applications still, apparently. Didn't work for my sample, though.
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