Board Thread:General Discussion/@comment-4161952-20130801170712/@comment-11051098-20131106110729

A Zanpakutô is a part of a Shinigami's soul. If the Shinigami dies, so does its Zanpakutô. When the captains mourned the death of Yamamoto after the first battle, they stood in front of a table holding the broken pieces of Ryûjin Jakka that was found.

Even if Ryûjin Jakka wasn't broken when its master died, I doubt Aizen would be able to use it as anything else than a normal sword, if he got his hands on it.

And for the record, everyone who were inside the Seireitei, appears to still be there. The only thing that changed is that the Seireitei was switched and replaced with the Wandenreich.