Minimization of Catalase Interference in Glucose Determinations with Immobilized Glucose Oxidase

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Abstract
Catalase, coimmobilized with glucose oxidase in an open, nylon tube, can decompose hydrogen peroxide and reduce the sensitivity of continuous flow glucose determinations. Millimolar concentrations of sodium azide display mixed-type noncompetitive inhibition of catalase. Because of this, the assay sensitivity can be improved by a factor of .gtoreq. 4 by adding azide. Azide does not affect the Trinder/peroxidase [EC 1.11.1.7] color-forming reaction but does inhibit glucose oxidase noncompetitively with an inhibition constant of 18 mM. Significant amounts of catalase are indicated by a nonlinear relationship between instrumental response and reactor length. Upon addition of 1 mM azide to the reaction manifold, the response becomes directly proportional to the reactor length (0-50 cm).