Hydrogen Bond-Based Macrocyclic and Tripodal Neutral Ionophores for Highly Selective Polymeric Membrane Sulfate-Selective Electrodes

Four hydrogen bond-based macrocyclic and tripodal neutral receptors with increasing conformational complementarity with sulfate were used for the first time as ionophores to develop polymeric membrane sulfate-selective electrodes. Optimizing the membrane composition such as ionophores, lipophilic additives, and plasticizers yielded ISEs which showed Nernstian response to sulfate with the best selectivity so far and improved detection limits (a slope of -29.8 mV/dec in the linear range of 1 X 10(-6) -1 x 10(-1 )M with a detection limit of 5 x 10(-7) M), which led to the success of the determination of sulfate in drinking water samples and neomycine tablets. The anion-ionophore complex constants in the membrane phase were determined and correlated with the selectivity sequence of the ISEs. Studies on the influence of pH of the sample solution demonstrated that the developed ISEs can be operated in a wide pH range of 3-8 with fast response and rapid (in 1 min) and long lifetime. The success of these ionophores represents a feasible strategy for overcoming the Hofmeister series by employing a combination of complementarity and hydrogen bonds.

Automated summary

This study utilized four hydrogen-bond based receptors as ionophores to develop polymeric membrane sulfate-selective electrodes, achieving the best selectivity and improved detection limits for sulfate. By optimizing the membrane composition, the anion-ionophore complex constants in the membrane phase were determined, and the electrodes demonstrated fast response and long lifetime over a wide pH range. The success of these ionophores in determining sulfate content in various samples showcases the potential of utilizing complementarity and hydrogen bonds to overcome selectivity challenges.