THE INFLUENCE OF FLOW-RATE ON BIOSENSORS BASED ON REDOX ENZYMES INCORPORATED IN A REDOX POLYMER MOUNTED IN A THIN-LAYER FLOW CELL

Enzyme electrodes, based on redox enzymes immobilized in redox polymers at electrode surfaces, were mounted in a thin-layer flow cell. The catalytic currents at different flow rates and concentrations for a continuous flow of substrate solution were measured and compared with the peak currents for injections of a plug of substrate solution, under corresponding conditions. The catalytic steady-state current for continuous-flow measurements increased with increasing flow rate, i.e., with increasing convection. When there was no appreciable depletion of substrate, the response was not altered by flow rate. For injected plugs of substrate, the peak current was dependent both on convection and on the time of contact between electrode and substrate solution. For enzymes with a low K'm, depletion effects dominate, and higher responses follow high flow rates, while the time of contact dominates for enzymes with high K'm, leading to higher peak currents with decreasing flow rate. © 1993 Academic Press, Inc.