The performance of a cyhndncal enzyme electrode with a soluble mediator was analysed theoretically The normahzed current response was calculated at various values of both the electrode radius (a) to enzyme layer thickness (I) ratio, a/l, and the relative catalyttc actwtties, as and a, (= (k,,[E]Iz/KMs M DsM)'/2) The calculated results demonstrated that at high mediator mncentratlon, larger a/l ratio and increased relative catalytic actMty for the substrate, as, a wder linear range could be obtamed for a calculated glucose calibration graph However, the hneanty was found to be less dependent on a/l than es Altematnrely, at htgh glucose concentration, the medator concentration -response curve calculated at low a/l values and a high catalytic actlvlty for the mediator, Ok, indicated a \krlde linear range Immobdlzed glucose ozodase (GOD) cyhndrlcal microelectrodes were fabncated and then charactenstics were evaluated by using 1,Cbenzoqumone as electron mediator GOD was munobthzed m a photo-cross-hnkable polymer on two types of cyhndncal microelectrodes of 2 and 25 km diameter The linear ranges of the observed calibration graphs were wder than that obtained using a disc electrode of 1 mm diameter Thus was probably due to the larger os values obtamed wrath the glucose sensors of 2 and 25 pm diameter Moreover, the response of the 2-pm glucose sensor based on hydrogen peromde detection was compared with that usmg mediators This result showed that the wider measurable range was obtamed usmg mediators Keywords Amperometry, Glucose, Microelectrodes. Mediators Many special features have stimulated a broad research effort mto the behavlour of ultrarmcro voltammetrlc electrodes [l-4] These unusual ' Present address Teknologue Co, l-26-2 Tamagawa, Chofu-slu, Tokyo 182, Japan * Present address Mem Selka Kalsha, 5-3-1 Chiyoda,
properties mclude multi-dlmenslonal dtislon and low 1R drop between electrodes Therefore, a steady or quasi-steady-state current can be obtamed with a stationary electrode Also, a twoelectrode configuratloi and a low-conductrvlty system can be applied to electrochemical measurement Moreover, owmg to Its very small size,