Separation Iridium from Rhodium

I need information on separation of Iridium from Rhodium by using NH4Cl and using Hydrgen peroxide as an oxidizing agent. Process Map( pump dissolved liquor to a reator in a Chloride form that is Rhodium Chloride and Iridium Chloride in a 3+ oxidation state, the intent is to oxidize the Iridium to a 4+ but suppressing Rhodium to a 3+ so as to make sure that as you precipitate the Iridium. The H₂O₂ is added at 80⁰C then add NH4Cl at 70⁰C. The problem is that this process is suppose to precipitate Ir only but it also precipitate Rh in the process, so I need help in order to keep Ir at a 4+ state and make sure that Rh is kept at 3+ so as to avoid co-precipitation of the later metal.