Development of a new photopolymerizable membrane for monochloroacetate sensitive potentiometric sensors

The composition of a monochloroacetate (MCA) sensitive membrane based on a new photocurable polymer is presented. The interest on measuring this parameter is based on its use in industrial processes for surfactants fabrication. The new polymer proposed, based on an aliphatic urethane diacrylate oligomer, has been chosen as membrane matrix due to its easy deposition procedure compared with PVC membranes. The deposition of the membrane and its photopolymerization under UV light is achieved in a few seconds. The membrane composition has been optimized in order to attain good mechanical properties and optimal sensor response by adjusting optimal ratio of monomer, cross-linker, ionophore and plasticizer. The MCA sensitive membrane has been tested using a potentiometric transducer based on an ah-solid-state design. The resulting sensors show a sensitivity of 55 mV per decade in a linear response range between 10(-4) and 10(-1) M MCA. The response time (t(95%)) is 5 s and its lifetime under continuous operation is 90 days. Interference of usual ions is much lower than for PVC membranes, showing and improvement specially considering its future application in process monitoring. (C) 1999 Elsevier Science B.V. All rights reserved.