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I have begun a chemistry experiment that attempts to determine how iron content in spinach is affected by the length of time it is cooked. Through research, I learned that iron content is often determined through a redox titration with potassium permanganate. I prepared my own spinach extract by mushing, dissolving in acid, and boiling, and titrated it, but I'm getting way larger iron levels than I should be (1 mg as opposed to 0.1). I know that this is because of other metals in the spinach which are also oxidized. How can I narrow this down to just iron levels? Is there some stoichiometry I can use to estimate it? How can I modify my experiment to produce a more reliable trend?

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    $\begingroup$ This does not work as oxidation by permanganate is not specific for iron(II), as many organic compounds from spinach can be oxidized too. $\endgroup$
    – Poutnik
    Feb 8 at 14:30
  • $\begingroup$ How should cooking change the iron content? $\endgroup$
    – Karl
    Feb 8 at 20:47
  • $\begingroup$ Note that spinach contains oxalates that bind to iron, making determination difficult. Likely, you'd want to calcine the sample, removing organic chemicals. $\endgroup$ Feb 9 at 3:50
  • $\begingroup$ @Karl i plan to test the hypothesis that cooking spinach causes it to leach/lose its iron. cooking for longer periods of time may cause the spinach to lose its iron to the water, or, alternatively, it may begin to break down the oxalates and thus increase the iron content $\endgroup$
    – beebs
    Feb 20 at 16:37
  • $\begingroup$ @DrMoishePippik thanks for your advice. if calcining oxidizes the compound, how would this work with the titration? potassium permanganate is also an oxidizing agent, so if the iron is already oxidized from 2+ to 3+ by the calcification, i can't oxidize it again, right? like do i then have to re-reduce the iron somehow before titrating? $\endgroup$
    – beebs
    Feb 20 at 16:40

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