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

The feasibility of employing cloud point extraction CPE as extraction and preconcentration method for the recovery of herbicides from milk samples followed by high performance liquid chromatography HPLC analysis is demonstrated. An aqueous surfactant solution containing 60 g/L Tween 20 or Triton X-100 was heated with an appropriate concentration of NH4 2SO4 or NaCl for the extraction of herbicides. The extract was analyzed by HPLC subsequently. Six herbicides in milk were analyzed simultaneously. The results showed that the linear dynamic ranges of detection were 20 - 10 000 mu g/L for tralkoxydim metribuzin and bromoxynil 30 - 10 000 mu g/L for mefenacet and 50 - 10 000 mu g/L for bensulfuron-methyl and nicosulfuron. The correlation coefficients were 0. 998 1 - 0. 999 7. The average recoveries of the six herbicides ranged from 85. 09% to 96. 74%. The relative standard deviations for the six herbicides were in the range of 1. 90% - 3. 98%. The limits of detection for the six pesticides were lower than the maximum residue limits MRL of China. The results indicate that the method is easier faster sensitive and produces less pollutants.