Abstract: This paper reports on the design and performance of an electrolytic (amperometric), nonmembrane, three-electrode system with fast response to changes in dissolved oxygen concentration and specially suitable for use with solutions flowing in narrow tubing at constant rate. The device is of utility in situations where a fast response is needed such as in sample injection techniques in continuous flow analysis.

Abstract: The optical biosensor consisted of a special flow cell located in a conventional spectrophotometer; the inner walls of the flow cell were coated with an immobilized biocatalyst. Three flow injection manifolds are proposed for controlling the flow of sample solution through the biosensor: (i) a system in which the flow is halted while the sample plug is in the flow cell, (ii) a system in which the flow direction is changed iteratively, and (iii) an open - closed loop that permits the sample to be circulated continuously through the flow cell. The performances of these manifolds were compared by use of immobilized β-glucuronidase for the kinetic determination of 4-nitrophenyl β-D-glucuronide; the 4-nitrophenol produced was detected at 405 nm. The optimized operating parameters for each manifold are given. By comparing sensitivities, α-coefficient and sampling frequencies, it is concluded that manifold (ii) is marginally superior to manifolds (i) and (iii).