Dear Archana,

This kind of titration is based on the reduction of all Co in the material to Co2+. There are many techniques, and not all of them are iodometric. You can find different approaches in J. Mater. Chem. 2002 , 12 , 1761.

The overall procedure consists of the two steps. First, you have to find the total amount of Co per gram of the material, for example, by ICP. Then you do the titration, which gives you the amount of electrons that can be accepted by the 1g of the material. Taking into account that Co3+ accepts one electron, Co4+ takes two and Co2+ does not change, you can find the average oxidation degree of Co. Using the condition of the electroneutrality, you can find the deviation of the oxygen content from the stoichiometric one.

There are several papers on iodometric titration for manganites and cuprates (from the era of high Tc superconductors), where the iodometric titration procedure is given. You need to modify them for you sample and system. You can discuss it with analytical chemists and they should be able to help you out. Another way of identifying oxygen content is using neutron diffraction and or Mossbauer spectroscopy, if you are using cobalt samples. From the cation distribution you can calculate oxygen content also and also oxygen %. 

Thank you, Sir.