Raddogz - Yup, the stuff you can get at HD or ACE hardware. The original AP TWP cartridges are good for about 50 gallons or so only. So I saved several spent cartridges and separated and recharged the resins.
Now, I'm running the cationic and anionic exchange resins from 3 cartridges in 2 separate columns. I think I've run close to 100 gallons through them and the color change indicator is barely starting to turn blue. So I figure it'll be a long while before the next recharge. Sorry I don't have anything more specific than that.
Elite - Organics in the water are trapped by carbon. Particulates are trapped by a 5 micron filter. Other "stuff" in the tap water would be in the form of positive or negative ions which would be adsorbed onto their respective exchange resins.
Copper ions are +2 and +3 cations. Phosphate is -3 anion, Iron is +2 and +3, Nitrate is -2.
Chloramine, I believe, undergoes catalytic decomposition on contact with the carbon. The decomposition products are trapped by the resin. That's also why you can smell ammonia if your resin is completely exhausted. The trapped ammonia gets released.
Use the color change resin or test with a TDS meter, and recharge the resin before it's completely exhausted. Or else, swap a fresh cartridge in line after the used one. Then you can leave the first one in place until it's completely spent.