Minimization of Catalase Interference in Glucose Determinations with Immobilized Glucose Oxidase

Catalase, co-immobilized with glucose oxidase in an open, nylon tube, can decompose hydrogen peroxide and reduce the sensitivity of continuous flow glucose determinatinos. 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 four or more by adding azide. Azide does not affect the Trinder/peroxidase 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).