Supercritic CO2 as an extraction solvent

[asfd]

Last semester we extracted caffeine from tea with CH2Cl2 and we were told it's possible to do the same thing with liquid CO2. This is interesting but pretty hard to do since you need high pressure/low temp in order to get liquid CO2. My question is: would it be possible to use liquid nitrogen instead of CO2 to do the same thing?

[Gokul43201]

I'm pretty sure liquid N2 won't work anywhere near as well as liq. CO2.

The reason the CO2 is used is because it is a great organic solvent, not because it is a cold liquid. The problem of the liquid CO2 can be partially overcome by what is commonly known as CO2 snow. CO2 snow is used with great success in removing organic matter from micro-electronic chips. My lab considered buying this equipment for cleaning the chips we make, but the things are so @#$*^%& expensive ! :grumpy:

For more on this, simply Google "CO2 cleaning".