Thursday, January 12, 2012
Extracting caffeine with methylene chloride
In a previous video, I showed how to extract caffeinated water from green coffee beans with supercritical CO2. Here, I show how to extract dry caffeine crystals from the caffeinated water (ie coffee, in this case). I used a vacuum filtration setup to create very strong coffee, then mixed it with methylene chloride in a seperatory funnel. The methylene chloride sinks below the water, taking most of the caffeine with it. By opening the funnel carefully, only the methylene chloride and caffeine can be transferred to a flask where the methylene chloride is boiled away. I then mounted a test tube in a rubber stopped and filled the tube with ice. With the stopped in the flask, I evacuated the flask and applied heat. The caffeine will sublimate and collect on the cold test tube. I scraped off the caffeine and measured the mass.
The brown stuff is (maybe) tannins. Heating on a hotplate gently can help. When everything goes just right, you should see needles of caffeine form, generally pure white.
ReplyDeleteCaffeine is used as a melting point standard, and you can get a really good sense of how pure your stuff is by checking the melting point.
Methylene chloride is a suspected carcinogen.
ReplyDeleteIs there a way to extract tasteless caffeine?
ReplyDelete