Science Buddies: "Ask an Expert"

Hello,
I am an 8th grade student and I'm currently working on a project which requires me to measure caffeine levels in coffee. I did some research on how to do this and a spectrophotometer was one of the solutions that came up. But, none of the sites I searched up really explained how it measures caffeine amounts and what the steps were to do it in my understanding. My science teacher, who offered to let me use his spectrophotometer, also didn't understand how that would work. I would really appreciate it if someone could explain to me how this would work, what the steps are to do it, and if there are any other accurate methods. Thank you!

Hello mayareid808,

A spectrophotometric analysis seems to be the main method for measuring the amount of caffeine in a solution. After a bit of searching I found a few articles with descriptions of the method. One of these is at this link:

http://maxwellsci.com/print/ajfst/v6-155-158.pdf

The basic steps in the method are 1) calibration of the UV spectrophotometer, 2) extraction of the caffeine from beverage samples and 3) testing the extracted caffeine.

The calibration step defines the amounts of UV light absorbed by caffeine solutions of different concentrations. The UV absorbance measured for caffeine from a beverage is used with the calibration data to calculate the caffeine concentration in the beverage.

The test method is not all that difficult but the caffeine extraction involves a solvent that requires safe handling precautions during use and safe disposal after use. If you decide to try this test method I suggest that you ask your teacher or someone else who has experience with handling solvents to help you with the appropriate procedures.

I hope this helps and good luck with your project. Please post again if you have more questions.

A. Norman