Determination of Melamine in Milk Using Cloud Point Extraction-High Performance Liquid Chromatography

A method for the detremination of melamine from milk samples was developed by cloud point extraction combination with high performance liquid chromatography(HPLC).Triton X-100 was used for demulsification of milk in the presence of trichloroacetic acid.Surfactant of PEG-600 was used as extractant and the extraction efficiency of melamine was studied.The optimum conditions of demulsification and CPE were as follows:concentration of Triton X-100:20 g/L;concentration of CCl3COOH:20 g/L;heating temperature:100 ℃;heating time:10 min;concentrations of PEG600,Na2CO3 and Na2SO4 were 130 g/L,5 g/L and 260 g/L,respectively;equilitration temperature:70 ℃;equilitration time:30 min.Under the optimal conditions,the calibration curve was linear for melamine concentration in the range of 0.4-80 mg/L with corelation coefficient of 0.999 8.Spiked recoveries for the standard addition of melamine in the milk was in the range of 80%-98% with RSDs between 1.2%and 5.7%.The limit of detection for melamine was 0.9 mg/kg.The method shows advantages of simplicity,high sensitivity and less pollutants.