Evaluation and single laboratory validation of an on-line turbulent flow extraction tandem mass spectrometry method for melamine in infant formula

This report presents the single-laboratory validation of a method for the determination of melamine in dairy-based products using on-line turbulent flow extraction-tandem mass spectrometry. Liquid or powder test portions were dissolved in water, enriched with (13)C(3)(15)N(3)-Melamine internal standard, followed by protein precipitation and withdrawal of an aliquot for analysis. The turbulent flow method was validated by analyses of liquid and powdered proficiency test portions containing up to 10mg/kg melamine. Accuracy of results ranged from 96 to 106% of the assigned values for the 6 proficiency test portions tested with relative standard deviations of 4-8%. Apparent recoveries based on addition of amino-(15)N(3)-Melamine to prepared test portions were between 98 and 114%. Based on the repeat analysis of a known blank sample the limit of detection and limit of quantification were determined to be 27 and 87 μg/kg, respectively. Additionally, this report demonstrates that turbulent flow chromatography is significantly faster than traditional LC-MS, with sample analysis times of less than 2 min.