Abstract: A simple, rapid method for the determination of melamine in milk and milk powder was developed using QuEChERS approach coupled with weak cation exchange chromatography (WCX). The samples were extracted and cleaned-up by medicinal alcohol and lipid adsorbent (LAS) simultaneously, then centrifuged and filtered for high performance liquid chromatographic (HPLC) analysis. The separation was performed on a WCX column (150 mm×4.6 mm, 5 μm) with 2 mmol/L KH2PO4 (pH 3.8) as mobile phase. The flow rate was 1.5 mL/min and the detection wavelength was 208 nm. The injection volume was 20 μL and the column temperature was 30 ℃. Under the optimized conditions, good linearity was obtained in the range of 0.02~20 mg/L with a correlation coefficient (r2) of 0.9999. For samples spiked with melamine standard in the range of 1~50 mg/kg, the average recoveries of standard in the milk and milk powder were 98.9%~105.2% and 86.4%~102.9%, respectively. The relative standard deviations were 0.9%~3.4% and 1.5%~6.7%, respectively. The limits of detection (LOD, S/N≥3) were 0.05 mg/kg (milk) and 0.1 mg/kg (milk powder). The present method is green due to not use of the toxic organic solvents.

Key words: milk, milk powder, QuEChERS, rapid analysis, weak cation exchange chromatography (WCX), melamine