Residue analysis of melamine in milk products by micellar electrokinetic capillary chromatography with amperometric detection

A high-performance micellar electrokinetic capillary chromatography with amperometric detection (MECC-AD) method for the fast determination of melamine (MM), occasionally used to increase the apparent protein content of milk products, has been developed. Method development involved optimisation of the working electrode, the running buffer system and acidity, the concentration of sodium dodecyl sulphate (SDS), the separation voltage, the applied potential and the sample injection time. Under the optimum conditions, MM can be well separated from its co-existing interferences in real-world samples within 9 min at the separation voltage of 20 kV in a 8 mmol/L SDS/20 mmol/L H₃BO₃-Na₂B₄O₇ running buffer (pH 7.4). Satisfactory recovery (83.3-105.5%), repeatability of the peak current (3.2%) and migration time (3.8%), and the limit of detection (2.1 × 10^-6 g/mL) for the method were achieved. This proposed procedure has been successfully used for the determination of MM in milk products.