QUANTIFICATION OF MELAMINE IN MILK AND DAIRY PRODUCTS BY LIQUID CHROMATOGRAPHY AFTER A SIMPLE SAMPLE CLEAN-UP PROCEDURE

In this work, a simple procedure of melamine determination in dairy products is reported. This is based first on melamine extraction from dairy products by 1% acetic acid, sonication, centrifugation and filtration by 0.45 mu m filter. The proposed method has a low detection limit (0.50mg kg(-1)), high accuracy (%recovery 98.9%), high precision (%RSD range 1.6-2.5%), high calibration sensitivity (19,335 (mg l(-1))(-1)), and a wide dynamic range (1.0-50.0mg l(-1)). Melamine was accurately quantified in spiked powdered milk, infant powder milk, full-fat liquid milk, fat-free liquid milk, local yoghurt, and local soft cheese (spiking levels 0.5, 50, and 1000 mg kg(-1)). The samples have variable amounts of fat (0-29%) and protein (3-23%) indicating the wide applicability of the proposed method. The %recoveries with %RSD were 78.2-103.6(2.5), 92.7-98.8(4.7), 79.3-101.5(3.8), 86.3-101.0(2.6), 78.0-89.2 (8.3), and 91.8-103.8(3.2) for soft cheese, yoghurt, powdered milk, infant powder, full-fat liquid milk, fat-free liquid milk, respectively.