AbstractVarious flow‐injection analysis arrangements employing immobilized oxidase and peroxidase enzymes in conjunction with fluoride ion‐selective electrode detection are described. Selective measurement of substrates is based on the oxidase‐catalyzed production of hydrogen peroxide. The liberated peroxide is detected via a coupled peroxidase reaction involving a fluoroaromatic reagent added to the carrier stream to yield free fluoride ions. Three specific arrangements are evaluated: (1) both enzymes coimmobilized on a single membrane covering the fluoride electrode detector, (2) both enzymes immobilized on controlled‐pore glass within a flow‐through reactor place before the potentiometric detector, and (3) two separate enzyme reactors placed in series upstream from the electrode. Optimum sensitivity toward model analyte glucose using glucose oxidase is achieved with arrangements based on the immobilized enzyme reactors. With these systems, detection of glucose at concentrations ranging from 0.1 to 10 mM is possible at throughputs of more than 30
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