Simultaneous determination of Fe(III) and Fe(II) in water solutions and tissue homogenates using desferal and 1,10-phenanthroline.

At neutral pH values 1,10-phenanthroline forms a colored complex with Fe(II), but it does not form such a complex with Fe(III). On the contrary, only Fe(III) forms with desferal a yellow complex with a g = 4.3 electron paramagnetic resonance (EPR) signal, but Fe(II) is rapidly oxidized by desferal to Fe(III), which gives then a yellow complex. On the basis of these facts, a method for simultaneous determination of both Fe(II) and Fe(III) ions was elaborated using a desferal-phenanthroline mixture. Two ways of detecting Fe(II) and Fe(III) have been suggested: (1) the spectrophotometric method for transparent water solutions, and (2) the EPR-spectrometric method for turbid solutions and tissue homogenates. The latter method was applied for determination of free and weakly bound iron in rat liver. The Fe(II) amount in intact liver was 22.2 +/- 7.6 nmol/g of wet tissue; free Fe(III) was not found.