Apothecary Antonivich is a level 60 master alchemy trainer and reagents & poison vendor located at Thrallmar in the contested territory of Hellfire Peninsula. He teaches alchemy up to 375 skill.
He starts the following quests:
[60] A Burden of Souls- [61] Report to Nazgrel
- [61] The Demoniac Scryer
The following quests are no longer available as of Cataclysm:
- [70] Master of Elixirs
- [70] Master of Potions
- [70] Master of Transmutation
For Master of Transmutation: It looks like you must be at 475 alchemy in order to make the quest available, at which point you can pick it up from an alchemy trainer in a major city. (Note from Eryenis on 2011/12/04, Patch 4.3.0 courtesy of Wowhead)
See List of Hellfire Peninsula NPCs.