High Performance Capillary Electrophoretic Determination of Melamine in Milk Products

A new method for the rapid determination of melamine in milk products by high performance capillary electrophoresis (HPCE) with diode array detection was established. Samples were extracted with 100 mmol/L acetic acid. The chromatographic separation was carried out in an uncoated fused-silica capillary [20 cm (effective length) ×50 μm] using 150 mmol/L NaH2PO3 as a separation buffer. Melamine was detected at 235 nm and quantified by peak-area external standard method. The effects of buffer concentration, running pH and sample pretreatment conditions on HPCE detection of melamine were investigated. The LOD and LOQ of the method were 0.06 (S/N=3) and 0.2 mg/L (S/N=10), respectively. The linear range was from 0.2 to 200 mg/L with a correlation coefficient of 0.9998. The average spiked recoveries of five replicates at two levels (1.0 and 10 mg/L) were 93.0% and 84.3%, respectively. The analysis could be completed within 6 min (2 min for rinsing plus 4 min for separation). The HPCE method is time- and solvent-saving, and environment-friendly, and has a good accuracy. Therefore, it can be used for the routine determination of melamine in milk products.