Assessing redox properties of standard humic substances

S. Rakshit, D. Sarkar

Research output: Contribution to journalArticlepeer-review


Redox properties of humic substances (HS) control important biogeochemical processes. Thus, accurate estimation of redox properties of HS is essential. However, there is no general consensus regarding the best available measurement method of HS redox properties. In this study, we compared several common HS redox property measurement methods using anthraquinone-2,6-disulfonate (AQDS) as model compound, and standard Elliot soil humic acid (1S102H, ESHA), reference Pahokee peat (1R103H, PPHA), and Suwannee River natural organic matter (1R101N, SRNOM) as representative HS. We found that the H2/Pd reduction method followed by incubation with ferric citrate (FeCit) reagent was incomplete, and the H2/Pd reduction method followed by incubation with potassium ferricyanide (K3Fe(CN)6) was insensitive. Stannous chloride (SnCl2) reduction followed by titration of excess stannous (Sn2+) by potassium dichromate (K2Cr2O7) was found to be most accurate. These findings will help in future investigations on detailed characterizations of functional groups of HS responsible for oxidation/reduction reactions.

Original languageEnglish
Pages (from-to)1497-1504
Number of pages8
JournalInternational Journal of Environmental Science and Technology
Issue number7
StatePublished - Jul 1 2017

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • General Agricultural and Biological Sciences


  • Electron shuttle
  • Humics
  • Quinone
  • Redox

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