The influence of alumina type on the immobilization of Ascorbate oxidase and ascorbic acid detection

Abstract

Two alumina types (trihydrate (T) and anhydrous (G)) were used for the immobilization of ascorbate oxidase (AO) by the adsorption procedure. The samples were characterized by FTIR analysis and EPR spectroscopy to confirm the presence of enzyme in the composite and the activity of immobilized enzyme. The samples of alumina with and without AO were used as modifer of carbon paste electrode and tested by Fe(CN6)3-/4-redox probe using cyclic voltammetry at different scan rates. The response of investigated electrodes toward ascorbic acid was tested in the Britton-Robinson buffer at pH range of 2 to 5. Direct detection of ascorbic acid was tested at G and G+AO electrodes and the calibration curves were constructed by square wave voltammetry under the optimized conditions. The immobilization of AO at anhydrous alumina increased the concentration range and the sensitivity from 0.00617 μM/μA for G to 0.01693 μM/μA for G+AO in the concentration range from 10 μM to 200 μM.