A thin-layer twin-electrode electrochemical cell in which the working
and auxiliary electrodes are facing each other and which contains the
appropriate enzyme and a mediator was used for the determination of ch
olesterol or glucose. A steady-state diffusion-controlled response was
obtained for cholesterol whereas for glucose the response was limited
by diffusion and kinetics. Simulation of the system showed that a ste
ady-state response is obtained, in the absence of kinetic complication
s, after a time of 0.01 d2/Ds, where d is the distance between the two
electrodes and D is the diffusion coefficient of the mediator. Linear
plots of steady-state current versus concentration were obtained for
cholesterol and glucose. The results were compared with those expected
theoretically and a thin-layer capillary fill device is proposed.