COPPER(II)-ION RESPONSE OF CU-AS-SE THIN-FILM SENSORS IN A FLOW-THROUGH MICROCELL

Chemical microsensors combined with Row-through and flow-injection ana lysis microsystems are promising analytical instruments for reliable, high performance environmental monitoring, medical applications and pr ocess control. In this report we discuss the sensitivity, selectivity, response time, and potential stability of Cu-As-Se ultrathin films (o btained by r.f. co-sputtering of the host glass and metallic copper) i n a flow-through microcell with a volume of approximate to 10 mu l. As expected, the Cu2+-ion response at micromolar concentrations is much better in comparison with static measurements, i.e., measurements done without stirring or moving the solution. Thin-film sensors exhibit ne ar-Nernstian response over six orders of magnitude with a detection li mit between 10(-8) and 10(-7) M. The better detection limit of the sen sors in the Row-through cell causes improved apparent selectivity at l ow Cu2+ concentrations in the presence of high alkali and alkali-earth cation concentrations. It was quite unexpected that we could observe a better selectivity (by a factor of 100) in the presence of Cd2+ ions as well as Ni2+, H+ and Fe3+ cations. Possible reasons for such behav iour are discussed.