Study of the influence of polymeric membrane composition on the sensitivity of acoustic wave sensors for metal analysis

Selective polymeric membranes have shown to be adequate to manufacture ion selective electrodes and acoustic wave sensors for metal analysis. The present work was carried out to study the influence of the composition of the polymeric membrane on the sensitivity of acoustic wave sensors. Data acquisition and PC storage allowed to compare the magnitude and shape of the frequency signals for membranes of several compositions. A complete characterization of the coated piezoelectric quartz crystals has been undertaken using an impedance/network analyser, and the coated crystals have been inspected by optical microscopy. Glass transition temperatures of the membranes have also been determined. Data helped understanding the role played by the plasticizer and the lipophilic salt, and agrees with the membrane composition preferences empirically established in the past.Results from this study allowed concluding that significant changes should be made on the composition of the membranes already reported in the literature for calcium and sodium bulk acoustic wave sensors, namely the replacement of low molecular height PVC by high molecular weight polymer and the use of DOS for sodium sensor and NPOE for calcium sensor.