Improving the Upper Detection Limit of Potentiometric Sensors.

In this work the problem of upper detection limit of potentiometric sensors is addressed. Due to deviation of potentiometric plots from cationic Nernstian responses determination of analytes like silver cations in concentrations above 10⁻² M is hardly possible, especially in the presence of background electrolyte containing lipophilic anions. Herein proposed approach applied classical complexing ligand, dithizone, attached to gold nanoparticles as ionophore. Immobilization on gold nanoparticles surface effectively anchores ligand molecules within the membrane phase. Thus obtained sensors are characterized with stable, Nernstian, potentiometric responses and selectivity comparable with classical membrane compositions. Moreover, due to lower formation constant of Ag⁺ with dithizone based ligand, herein reported sensors offer linear, Nernstian responses also in the range of high activity of AgNO₃ solutions. [ABSTRACT FROM AUTHOR]