Phosphate and arsenate electro-insertion processes into a N,N,N ',N'-tetraoctylphenylenediamine redox liquid

Frank Marken, Colin M. Hayman, Philip C. Bulman Page

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The electro-insertion of ions is a well-known phenomenon, which allows the transfer of anions or cations across phase boundaries to be monitored and driven electro-chemically. Extremely hydrophilic anions, such as phosphate and arsenate, are not usually observed to undergo electro-insertion. It is shown here that at organic redox liquid\ water/electrode triple interfaces these anions can be forced electro-chemically to transfer into organic media. The transfer process of phosphate anions from aqueous buffer solutions into organic microdroplets of the redox liquid N,N,N',N'-tetraoctylphenylenediamine (TOPD) is pH and concentration sensitive. It is shown that phosphate is transferred in the form Of PO4HK- in the presence of phosphate buffer. Two distinct potential regions are identified and attributed to (i) interfacial redox processes at the liquid/liquid interface associated with deprotonation and (ii) bulk redox processes associated with anion transfer from the aqueous to the organic phase. The comparison of phosphate and arsenate electro-insertion processes suggests that arsenate is less hydrophilic and transferred into the organic phase preferentially. (C) 2002 Published by Elsevier Science B.V.
Original languageEnglish
Pages (from-to)462-467
Number of pages6
JournalElectrochemistry Communications
Issue number5
Publication statusPublished - 2002


  • electro-insertion
  • voltammetry
  • triple phase boundary
  • arsenate
  • phosphate
  • ION
  • liquid vertical bar liquid boundary
  • ion exchange

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