• colorimetry;
  • extraction;
  • fluoride;
  • receptors;
  • water chemistry


Two new receptors R1 and R2 based on triphenylphosphonium salts with an active methylene group as binding site have been designed and synthesised for the detection of F ions. The detection limit of these receptors in organic media was found to be 0.2 ppm. Upon adding F ions, a Δλmax of 188 nm and 256 nm was observed for receptors R1 and R2, respectively. The detection process followed deprotonation of the methylene proton, which has been confirmed by 1H NMR titration. The receptors were evaluated for real-life applicability by extracting F ions from aqueous media and seawater into organic media. Receptor R2 was able to extract F ions from seawater with 99 % efficiency. The level of F ions present in seawater has been quantified and found to be 1.4 ppm, which is comparable to the reported literature value.