Composite Polyacrylate−Poly(3,4- ethylenedioxythiophene) Membranes for Improved All-Solid-State Ion-Selective Sensors

Abstract

A novel type of self-plasticizing polyacrylate-based membrane was developed for all-solid-state ion-selective potentiometric electrodes. The membrane composition contains a conducting polymer (CP): poly(3,4-ethylenedioxythiophene) end capped with methacrylate groups, chemically grafted with the membrane during the photopolymerization step. This composition results in ion-selective membranes with the following advantages: lower electrical resistance compared to the CP-free membrane, facile ion-to-electron transduction between the membrane and the electrode support, controlled low activity of analyte ions, and high concentration of interferent ions (incorporated with the CP) within the membrane, potentially resulting in improved analytical parameters. Ca2+- and K+-selective membranes were chosen as model systems to study the effect of pretreatment and CP content on the potentiometric sensor's characteristics. For Ca2+ sensors, reproducible and stable Nernstian characteristics were obtained within the range from 0.1 to 10(-9) M CaCl2, without a time-consuming preconditioning step. For K+-selective sensors, the influence on Nernstian response range was observed for varying KCl concentrations in the conditioning solution, with the lowest detection limit found close to 10(-8) M KCl. Mass spectrometry coupled with laser ablation studies of the membranes revealed that in this case the detection limit is not related to primary ion content in the membrane contacting a sample solution, but is affected by interfering ion concentration close to the membrane surface.