Btw yeah It could be from CWE. There is another method using acetone that I'll explain since a lot of people have trouble with the CWE.
First if you CWE the acetaminophen/codeine/caffeine tablets, you will find that you need an awful lot of water. Supposedly the aspirin tablets are better in terms of being able to put a little bit of water in a syringe with the powder and just squeeze the codeine water right out. Anyway. I just dont recommend drinking the water from CWE, because you still get a lot of acetominophen and caffeine. You can repeatedly evaporate it till there is little water and that will guarantee very little other crap, but you need to calculate solubilities.
Acetone - you can shake the tablet powder with acetone, enough to dissolve all the acetominophen and caffeine, povidone, etc, it will need to be a lot of acetone, depending on the amount of tablets. Say 500ml depending. You need to find out about solubilities. Codeine salt will not dissolve (almost none), so the precipitate will be just codeine salt. But make sure you weigh it to make sure there isn't more precipitate than there can be codeine. Then you've obviously got other stuff.
Back to CWE: There is also a method where you can evaporate CWE water to dry powder, then wash with methylene chloride to remove the caffeine, which it dissolves. That's what is used to decaffeinate coffee (or trichloroethylene but they are very similar solvents).
I think that doing a CWE to remove most acetominophen first, then drying and washing the resulting powder with acetone will give the best results. You'll get just codeine. Still better weigh it to be sure. Be sure you don't ingest any acetone - better be completely evaporated.
I can make it clearer if anyone cares.