As shown in Fig. 4a, the resulting color intensity is linear with the concentration over the range of 2.4 × 10−3 to 11.4 × 10−3M with a LOD of 8 × 10−4M for glucose in the serum samples. Different concentrations of glucose in the serum samples were achieved by adding glucose to a known concentration of 2.4 × 10−3M in the serum samples. The serum which have known the concentration of 2.4 ×10−3M of glucose was obtained from the hospital and tested by Roche automatic clinical chemistry analyzer. The results of the proposed method are consistent with that of Roche automatic clinical chemistry analyzer. The mean intensity was shown in the calibration curves in Fig. 4b. The equation of curve was y = 6.16
x + 87.94, R2 = 0.990.