Hi Zaini,
There is a little bit of Iron in almost everything we consume. However, it is the quantity that matters. Fresh extracted Wheat Grass juice contains more Iron compared to the spray or the pill which you can use instead of the juice. However, if you are faithful to your chelation, then you don't have to worry much about it.
As for the extracted juice, the daily dose is usually less than half a glass which does not contain significant amount of Iron. Trust me, that no one will even want to drink several glasses of that stuff (Yuck!) when the amount of Iron starts to matter.
Take care.