The Use of Chemical Sensor Systems for Sampling, Selectivity and Speciation

Chemical sensors are ideally suited to miniaturisation and reformatting in order to conform to particular types of flowing, static and low volume samples. An important additional need is the complementary tailoring of a measurement cell in order to create a functional, integrated sensor-based measuring system. In this context the importance of sampling, membrane barriers, electrode modification and transduction strategy have been outlined and specific examples provided. A description of the sampling technique, open micoflow, is given which demonstrates how measurements can be performed in colloid containing samples without associated sensor fouling. The permselectivity and porosity of microporous and homogeneous barrier membranes can be tailored by addition of suitable modifiers (eg. surfactant) to alter hydrophilic/hydrophobic properties. Specifically, this has facilitated the control of solute flux and permselectivity towards neutral, charged, polar or non-polar species. Ultrathin non-conducting electropolymerised films are an alternative route in creating permselectivity barriers. It is shown that by judicious choice of monomer derivative both permselectivity and functionality can be achieved. Impedance spectroscopy and spectral reflectance as sensor transduction strategies have been explored in specific relation to ligand containing conducting polymer films. Such techniques have enabled enhanced sensitivity and selectivity to be achieved which can be extended to a wide range of chemical sensor applications.