Detection of subnanomolar melamine based on electrochemical accumulation coupled with enzyme colorimetric assay.

Based on the synergetic effect of the electrochemical accumulation process and the signal amplification of enzymes, a new sensitive method has been developed for the detection of subnanomolar melamine. There are two steps involved in the sensor construction process: (1) accumulation of melamine on an electrode by cyclic voltammetric method and (2) chemical coupling of horseradish peroxidase (HRP) with the accumulated melamine through the linkage of glutaraldehyde. The coupled HRP catalyzes the oxidation of guaiacol to generate an amber-colored product. Quantitative analysis of melamine is performed by measuring the absorption intensities of the colored product. Under the optimal conditions, the method showed a wide linearity in the concentration range from 1.0 × 10(-11) to 1.0 × 10(-8) M for melamine detection. Moreover, it has been successfully applied to detect melamine in different infant formula powders and fish feed samples.