UREA POTENTIOMETRIC BIOSENSOR BASED ON ALL-SOLID-STATE TECHNOLOGY

A new urea potentiometric biosensor based on an all-solid-state (witho ut inner liquid contacts) technology has been developed. Potentiometri c transducers consisting of selective poly(vinyl chloride) (PVC) membr anes directly applied onto electrically-conducting composite materials ([0-3] graphite/epoxy composites) has been previously developed in ou r laboratory. This all-solid-state construction procedure has been ext ended to the preparation of urea potentiometric biosensors using a new enzyme-immobilization technique based on the deposition of the biocat alyst layer onto the active transducer surface by spraying a diluted s olution of glutaraldehyde. The combination of these new simple technol ogies provides a wide range of adaptability and multifunctional design s for the resulting sensing devices. Furthermore, by using a PVC-matri x membrane as the support of the enzymatic layer, the detachment of th e enzyme (urease) is considerably reduced since a better adsorption on the enzyme layer is achieved. The results obtained with this new type of urea potentiometric biosensor show a low response time (10 s) and a wide linear range (10(-5) to 10(-3) M) with a sensitivity of 55 mV p er urea decade. A great gain is achieved in terms of stability with a lifetime of about 40 days in periodical calibration use. Additionally, a flow-through urea biosensor using the same type of potentiometric t ransducer and immobilization procedure has been constructed for the us e in flow-injection analysis systems.