Interference of ferric ions with ferrous iron quantification using the ferrozine assay

J Microbiol Methods. 2013 Dec;95(3):366-7. doi: 10.1016/j.mimet.2013.10.005. Epub 2013 Oct 16.


The ferrozine assay is a widely used colorimetric method for determining soluble iron concentrations. We provide evidence for a heretofore unrecognized interference of ferric ions (Fe(3+)) on ferrous iron (Fe(2+)) measurements performed in the dark. Fe(3+) concentrations affected the absorbance measurements, which linearly increased with incubation time.

Keywords: Ferric; Ferrous; Ferrozine; Interference.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chemistry Techniques, Analytical*
  • Colorimetry / methods*
  • Darkness
  • Diagnostic Errors
  • Ferric Compounds / metabolism*
  • Ferrous Compounds / analysis*
  • Ferrozine / metabolism*
  • Ions / analysis
  • Iron / analysis*
  • Time Factors


  • Ferric Compounds
  • Ferrous Compounds
  • Ions
  • Ferrozine
  • Iron