Ion-selective electrodes for thiocyanate based on the dinuclear zinc(II) complex of a Bis-N,O-bidentate Schiff base

Phil Buhlmann, Lisa Yahya, Rolly Enderes

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

An ion selective electrode based on the dinuclear complex formed by two zinc(II) ions and two molecules of the bis-N,O-bidentate Schiff base 2,2′-[methylenebis(4,1-phenylenenitrilomethylidyne)]bisphenol exhibits thiocyanate selectivity with a good discrimination of nitrite, nitrate, and azide. The selectivities of electrode membranes with various compositions indicate that this potentiometric selectivity is based on the formation of a 1:1 complex between the thiocyanate anion and the dinuclear ionophore. The 2:1 ratio of thiocyanate ions and the dinuclear ionophore that results from higher ratios of cationic sites and ionophore worsens the selectivity, suggesting that binding of a thiocyanate to both zinc(II) centers of the dinuclear ionophore is not favorable. Interestingly, the selectivity patterns of these electrodes differ radically from that of a highly sulfate selective electrode based on a compound reported previously to be the analogous mononuclear 1:1 complex of zinc(II) and the same Schiff base. It is suggested that the previously reported 1:1 complex with zinc(II) may indeed have been a polymer of the same elemental composition.

Original languageEnglish (US)
Pages (from-to)973-978
Number of pages6
JournalElectroanalysis
Volume16
Issue number12
DOIs
StatePublished - Jun 1 2004

Keywords

  • Ion-selective electrode
  • Ionophore
  • Solvent polymeric membrane
  • Sulfate
  • Thiocyanate
  • Zinc(II) complex

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