Zero valent iron in nanoiron materials is the active agent, but usually nanoiron particles have an outer coating of iron oxides that are not capable of producing reactive ferrous ion.  The total amount of iron in nano-materials is typically measured through acid digestion and measurement of iron by atomic absorption or inductively coupled plasma-mass spectrometry; this method measures both zero valent iron and iron oxides.   A colorimetric method was developed using phenanthroline to react with ferrous as it was produced from dissolution of Nanofer 25S (mean particle size 87 nm).  Nanofer 25S is a commercially available nanoiron that is widely applied in environmental research for the oxidation of contaminants and toxicity evaluations. The colorimetric method involves adding Nanofer 25S to a solution of phenanthroline in acetate buffer, incubating for 10 minutes in the dark, and then measuring the color development at 510 nm; quantitative analysis was achieved with  comparing to a standard curve generated for varying concentrations of ferrous sulfate.  The method is highly reproducible.  When applied to Nanofer 25S, approximately 80% of the total iron was measured as ferrous iron.  Oxidized iron particles, and also ferric ion, were shown not to react with phenanthroline to produce an absorbance at 510 nm. The ferrous produced from Nanofer 25S was shown to have a better correlation with zero valent nanoiron oxidation of lipids than the measurement of total iron.

Rapid colorimetric method for determining production of ferrous from zerovalent nanoiron materials

248th National Meeting (2014)

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