Fig. 3. Selectivity of the proposed method for the detection of glucose. Each potential interfering substance was separately added into reaction solution in the absence of glucose. The concentration of glucose was 0.4 mM, and the concentration of the potential interfering substances was 8.0 mM. Inset: Typical photograph of glucose detection with the colorimetric method using GOx and papain as the catalysts (from left to right: glucose, maltose, lactose, fructose, urea, uric acid, ascorbic acid and blank).