The spectrophotometric determination of micromolar concentrations of Co2+ using o-phenanthroline

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8 Scopus citations


Co2+ and o-phenanthroline formed a 1:3 complex with absorption maxima at 346, 332, 313, and 301 nm. The complex obeyed Beer's Law at the first three maxima. Standard curves constructed by monitoring the E346 at different concentrations of Co2+ had a maximum sensitivity of about 1 μm Co2+. At this concentration of Co2+ the ΔE346 was 0.003 absorption units. This assay was not affected greatly by Ca2+, Mg2+, K+, Na+, or Tris. Erbium ions (Er3+) produced a small, nonspecific increase in absorbance at all wavelengths. Zn2+ also formed a complex with o-phenanthroline with maxima at 343, 328, and 313 nm. The absorbance of the Zn2+-o-phenanthroline complex was about 10% that of the Co2+-o-phenanthroline complex at 346 nm, but was still sufficient to cause interference at Zn2+ concentrations above 10 μm.

Original languageEnglish (US)
Pages (from-to)335-339
Number of pages5
JournalAnalytical Biochemistry
Issue number2
StatePublished - Dec 1983


  • cobalt
  • o-phenanthroline
  • spectrophotometry

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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