| Milk’s nutritional value is very high. It not only meet the nutritional needs of the elderly and children, but can invigorate health effectively. Nowadays, with the rapid development and residents’consumption level of China’s dairy industry, people’s consumption of milk has also been greatly improved. At the same time people put forward higher requirements for the safety of milk. There are many experimental results which had demonstrated that bisphenol A and nonylphenol exist in mineral water bottles, food packaging and medical devices. Modern medical studies suggest that bisphenol A and nonylphenol reaching a certain dose will threat to health. Studies show that alkylphenols bisphenol A (bisphenol A, BPA), nonylphenol (nonylphenol, NP) and other chemicals have shown a different estrogenic activity. Alkylphenol ethoxylates is an important non-ionic surfactant, which is widely used in household or. industrial detergents and plastic products, alkylphenol is its final degradation products.4-NP and BPA itself can serve as a chemical raw material, and also can be widely used in the production of multi-polycarbonate and epoxy resin, besides, in the production of plastics it can also be used as an antioxidant. So milk bag containing environmental estrogens bisphenol A and nonylphenol threaten the safety of dairy.Currently, the determination of bisphenol A and nonylphenol have been reported in the literatures. However, these methods mostly used large consumption of organic solvent, long operation time and have danger to human body and environment. Cloud point extraction technology as a new type of environmental, economical and efficient detection method can meet the requirements of high efficiency, economy and environmental protection. This paper introduce the principle and development of cloud point extraction technology, explore the concentration and extraction of bisphenol A and nonylphenol in milk and the conditions of HPLC detection and establish a CPE-HPLC detection method of BPA and NP. The main findings are as follows:(1) An analysis of Bisphenol (BPA) and Nonylphenol (NP) in Milk by Cloud Point Extraction was established. The experiment optimized the conditions for breaking and cloud point extraction.The optimum breaking condition:the use level of glacial acetic acidand anhydrous sodium sulfate was0.20mL and0.90g,5℃,10000rpm centrifuged for10min. The optimum cloud point extraction conditions:used100g/L Tween20aqueous solution as extracted surfactant, the addition amount of n-butanol was0.20mL and anhydrous sodium sulfate was0.20g, equilibrium at60℃for30min.(2)The experiment established a CPE-HPLC/UV detection analysis of bisphenol A and nonylphenol, optimized the mobile phase and HPLC conditions. Under the selected chromatographic conditions, used a mixed solution of acetonitrile mobile phase (A) and water (B) as the mobile phase, analysis the mixed standard solution of bisphenol and nonylphenol with Inertsil ODS-3(150mm×4.6mm,5μm) column at200nm under gradient elution. Elution procedure was:(A)45%for8min, then rose to65%, maintained for27min. Flow rate:1mL/min, column temperature:30℃. Bisphenol A and nonylphenol can be separated well under the optimized conditions, the peak wassym metrical and the interference of impurities in the milk and surfactant were avoided; The results showed that:the fortified recovery of bisphenol A was85.60-91.20%in the three supplement levels (0.05,0.10,0.20μg/mL), while, at the levels of (0.10,0.20,0.50μg/mL), the fortified recovery of nonylphenol was71.30-73.30%, and the standard deviation was3.42-9.85%. The results were accurate with higher degree of precision, and the processes were in line with the requirements of the detection of environmental drug residual, bisphenol A has good linear correlation in the range of0.05～2μg/mL while the range of the nonylphenol was0.10-10.00μg/mL, and both of the coefficients were higher than0.999; LOD value was2.23μg/kg-9.79μg/kg, it was below the limit requirement.(3) The experiment took the milk as the experimental substrate, using a new extraction method, cloud point extraction to extract the bisphenol A and nonylphenol in milk to solve the problems of traditional extraction methods. Researched and established a safe, economical, efficient analysis method, the method was also conform to the analysis of the residual of pesticide. |
