Validation of a method of high performance liquid chromatography with fluorescence detection for melamine determination in UHT whole bovine milk

A method of high performance liquid chromatography with fluorescence detection (HPLC-Fluo), based on previous studies of the natural fluorescence emission of melamine (250/365 nm), was developed and validated for melamine determination as an adulterant of bovine UHT whole milk. The clean up treatment of milk samples by deproteinization was thoroughly optimized. No matrix effect was observed and a linear range from 0.05 to 10.0 μg mL⁻¹ was obtained, with a value of R² equal to 0.9998. The limits of detection and quantification of melamine were 0.0081 and 0.027 μg mL⁻¹ respectively, or 0.023 and 0.076 μg g⁻¹ of milk, respectively, considering the sample dilution during extraction. Extracts of milk samples fortified with melamine at three concentration levels, two of which corresponded to the levels established by WHO for melamine in foods, led to an overall mean recovery of 95.4 ± 1.2% (n = 9). This recovery value satisfies the performance criteria established by the Codex Alimentarius for analytical methods suitable for determination of food residues, demonstrating the usefulness and effectiveness of the proposed method.