Single-run electrochemical determination of melamine in dairy products and pet foods

A simple electrochemical approach, which does not require any expensive and complex instruments, is established for the selective and quantitative recognition of melamine in diary products and pet foods. During a preconcentration step (at 1.8 V versus Ag/AgCl), the formation of a polymer film from melamine on a preanodized screen-printed carbon electrode was identified by SEM and XPS. The as-formed polymer was found to be electroactive with a reversible redox peak, and hence square-wave voltammetry was applied to further increase the detection sensitivity to meet the detection limit for application in real sample analysis. Simply with a medium exchange procedure, melamine was selectively detected with a detection limit (S/N=3) of 0.8 μM (i.e., 98.3 ppb) by square-wave voltammetry. Lower than 1 ppm of melamine in real samples can be easily detected with good recoveries of 98.7-100.9% by the proposed approach. The recovery tests established for external calibration and standard addition techniques verified that the analysis can be done in a single-run measurement.