A new calcium-sensor based on ion-selective conductometric microsensors - membranes and features

Based on the concept of ion-selective conductometric microsensors (ISCOM) a new calcium sensor was developed and characterized. ISCOM have a single pr obe, all-solid-state construction and do not need a reference electrode. Th ese sensors are amenable to miniaturization and integration in the true sen se of integrated circuit and microsystem technologies. The detection is acc omplished by measurement of the bulk conductance G(m) of a thin polymeric m embrane containing an ion-complexing agent, where the magnitude of G(m) can be related to the content of the primary ion in the analyzed solution. Thi n-film platinum electrodes forming an interdigitated electrode are used as the transducer to detect the conductivity of the polymeric membrane. Optimi zation of the membrane composition was carried out by testing different typ es of calcium-ionophores, polymers, and plasticizers. The sensor characteri stics have been investigated. The limit of detection is about 10(7) mol L-1 . The dynamic range is 10(-6)-10(1) mol L-1 with a response time of less th an 5 s. These parameters are comparable to those of corresponding potentiom etric calcium selective electrodes (ISE). The Ca2+-ISCOM demonstrates good practical relevant selectivities against typical interfering ions for biome dical and environmental applications.