Deploying hydrogen bond donor/acceptor on arylethynyl scaffold II: Urea based tripodal ionophores for polymeric membrane nitrate selective electrodes

Abstract

Along the line for developing ionophores by deploying hydrogen bond donor/acceptor on arylethynyl acaffold, two tripodal urea receptors were used as ionophores for the first time to fabricate polymeric membrane nitrate-selective electrodes. Replacing the hydrogens with fluorine atoms in the arylethynyl core facilitates the selectivity for nitrate over halides, originating from the additional anion–π interactions electron between nitrate and deficient fluorinated core. By optimizing membrane composition such as plasticizers and lipophilic additives, the proposed ISEs showed Nernstian response to nitrate with superior selectivity to both lipophilic ions and halides. Although the formation constants of anions-ionophore complex in membrane phase did not correlate well with the selectivity pattern of the ISEs, these data were consistent with that in solvent such as binary DMSO/CHCl3. The proposed ISEs could work in wide pH range solutions with short response time, good reversibility and reproducibility, which led to the success of determination of nitrate in real mineral water, tap water, as well as river water samples.