IP6 is not a true chelator like DMSA or DMPS. however i do believe it can grab free mercury and usher it out through the bowels. this is not the same as the work that DMSA does which will actually go collect mercury bound in tissues, bind to it, and usher it out.
the IP6 before and after is just to protect you from the mercury particles that get released during the procedure.
i had some info on IP6 and mercury, let me see if i can find it. i'll post tomorow.