Nitrate-selective electrode based on a cyclic bis-thiourea ionophore

Amanda S. Watts, Vasilis G. Gavalas, Arthur Cammers, Pilar Sánchez Andrada, Mateo Alajarín, Leonidas G. Bachas

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Compounds containing urea and thiourea groups can hydrogen bond oxoanions and, as such, represent a class of potential ionophores for anion-selective electrodes. We have evaluated cyclic and linear bis-thiourea compounds as ionophores in polymer membrane ion-selective electrodes. An improvement in the selectivity coefficient of nitrate against chloride of greater than one order of magnitude was observed with the cyclic ionophore in comparison to the Hofmeister lipophilicity series (log KN O3-, C l-pot of -3.50 with ionophore versus -2.40 with no bis-thiourea ionophore), indicating the preference of the cyclic ionophore for nitrate. This preference for nitrate over chloride may be attributed to the spatial arrangement of the thiourea hydrogen atoms, which are capable of forming hydrogen bonds with nitrate, as well as the size of the ionophore binding cavity. In the lowest-energy conformation, all thiourea hydrogen atoms point toward a putative nitrate binding site, likely contributing to enhanced coordination.

Original languageEnglish
Pages (from-to)200-207
Number of pages8
JournalSensors and Actuators, B: Chemical
Issue number1
StatePublished - Jan 30 2007

Bibliographical note

Funding Information:
Arthur Cammers is an Associate Professor of organic chemistry at the University of Kentucky. He earned a Bachelor of Science degree from the University of Wisconsin-Eau Claire and a doctorate in synthetic organic chemistry with Edwin Vedejs from the University of Wisconsin-MADISON. Arthur Cammers joined the faculty at the University of Kentucky after an NIH postdoctoral fellowship with Daniel Kemp at the Massachusetts Institute of Technology. Cammers is a NSF career awardee. His work focuses on solution and solid state hydrogen bonding, designing molecular recognition between molecules and at the nanometer scale. He has also investigated ring current anisotropy as a probe for molecular conformation.

Funding Information:
This work was supported by the National Aeronautics and Space Administration. ASW thank the National Science Foundation (IGERT) and the Research Challenge Trust Fund for fellowship support. PSA and MA thank the MEC-FEDER (Project CTQ2005-02323/BQU) and the Fundación Séneca-CARM (Project PI-1/00749/FS/01) for funding.


  • Bis-thiourea
  • Ion-selective electrode
  • Ionophore
  • Nitrate

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry


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