[Determination of melamine in milk and milk powder by high performance capillary electrophoresis]

A high performance capillary electrophoresis (HPCE) method has been established for the separation of melamine in milk and milk powder. The separation was carried out on a fused-silica uncoated capillary column (58.5 cm x 75 microm). The sample was injected by hydrodynamic injection (3.5 kPa (35 mbar) x 8 s) at a temperature of 25 degrees C. The analysis was completed in about 6 min in 40 mmol/L Na2HPO4-20 mmol/L citric acid buffer (pH 2.6) at 25 kV of separation voltage and 232 nm of detection wavelength. The linear range of melamine was 1 - 100 mg/kg, and the correlation coefficient was higher than 0. 997. The limits of quantification (LOQs) in milk and milk powder were 0.5 mg/kg and 1.0 mg/kg, respectively. The average recoveries were in the range of 72.2% -97.3% in the spiked range of the concentration of LOQs and 50 mg/kg, and the relative standard deviations were between 2.1% and 3.9%.