A flow-injection conductometric manifold equipped with an immobilized glucose-oxidase mini-reactor was proposed for the determination of glucose concentration. The glucose of the injected sample plug was oxidized enzymatically to its δ-lactone, and the hydrolysis of the lactone generated a concentration-dependent flow-injection signal. The dynamic range was from the tens of μM to the mM order of glucose; the immobilized enzyme reactor was stable for at least several months. The pH of the carrier solution was maintained in a slightly alkaline region (ca. 8.0 by 500 μM of Tris-HCl) to accelerate the spontaneous hydrolysis of δ-gluconolactone. The repeatability of the flow-injection signals was improved (CV < 3%, n = 7) by the addition of Triton X-100® (0.7% w/v) into the carrier solution.
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