How do I extract the iron inside vegetables(Squash and Spinach)?

I want to do an experiment about which vegetable has a greater iron content per serving but I don't know what are the steps to extract the iron to measure it nor can I find any tutorials on how to do so on the internet. If there are any common household materials that can be used that would be great but I know you still need some essential non-household materials to fully extract the iron in the vegetables. Thanks again in advance and I hope I get informative answers from you.