Purity - Activated Carbon/Caffeine Removal/Purity

[Incarnate]

Swim has used the cold water extraction technique several times with varying degrees of success, he currently strains the 80mls of solution of
40 8 mg tablets through a natural brown coffee filter, then when filtered, runs this through a basket of activated carbon grains, to remove caffeine (before drinking end product) Does activated carbon really reduce caffeine content in the final product? Does filtering the solution through the carbon cause a reduction in codeine content/quality?

any advice would be graciously appreciated.