Rapid Determination of Melamine in Milk Powder and Milk by Liquid Chromatography

Objective To establish a rapid method for detection of melamine in milk powder and milk.Methods Melamine in milk powder and milk samples was extracted in 20% methanol and 1% trichloroacetic acid by whirlpool mixed,ultrasonic bath at 30℃.The extracted solution was centrifugal purification at 4000 rpm at 4℃ and then was filtered through 0.45μm filter membrane before analysis by LC-DAD.The mobile phase consisted of 10 mmol/L sodium 1-hexane-sulfonate and 10 mmol/L lemon acid∶acetonitrile(92∶8).The melamine was separated by a column Agilent TC-C18(4.0 nm×250 nm,5μm) detected by liquid chromatography at 235 nm wave length,used retention time and ultraviolet spectroscopy for qualitative analysis and peak area for quantitative analysis.Results Used above extracted way,the established chromatography condition could achieve a better baseline separation for melamine from the matrix.The precision test showed that the RSD was less than 5%.The method linear ranges were from 0.500 μg/ml to 100 μg/ml,with the correlative coefficient of 0.999 5.The recoveries were from 81.2% to 112.1% added melamine in different milk powder.The detection limits for milk powder and milk were 2 mg/kg and 0.5 mg/kg,respectively.Conclusion Melamine in milk powder or milk is specifically detected for qualitative and quantitative analysis by LC-DAD.The method is characterized with accuracy,rapidity and efficiency,and it is suitable for the fundamental laboratories facing the mission to analyze mass of milk powder and milk samples.If necessary,a LC-MS/MS method was applied for validation.