| Animal husbandry is one of the foundations of the national economy, and it has good development prospects and growth potential. Whereas, with the development of animal husbandry, the excess of veterinary residues, which gradually pose dangers to environment and human health and bring a great effect on international trade, is frequently occurred. In recent years, many countries have established and increasingly perfected the determination system of veterinary residues in animal foods, maked lower maximum residue limits and more stricting standards. So it has more efficient, environmental-friendly, economical and quick requirement to ensure safety of food and meet the established determination system of many countries. Sulphonamides, one of antibiotics, are widely applied to animal husbandry, but the residues of sulphonamides have potential dangers to environment and human health. So many countries in the world have established maximum residue limits of Sas in foods of animal origin. Various analytical methods have been developed for the determination of Sas, but the preconcentration and clean-up techniques in these methods are time-consuming and present a threat to the environment and human health due to the use of organic solvents. Cloud point extraction can eliminate the above disadvantages as an environmental-friendly, efficient and economic determination. This paper particularly introduced the progress in CPE method technology and the method principle. This paper also studied extraction, purification and HPLC detection conditions of the target sulphonamides in milk, and developed an ideal analytical procedure based on CPE coupled to HPLC for the determination of the sulphonamides in milk. The main results are as follows:(i) In this research, we concentrated and separated seven target sulphonamides based on the method of CPE, optimized the effect factors in the procedure of de-emulsification and cloud point extraction. The most optimal effects of de-emulsification were that the volume of glacial acetic acid was 0.14mL, the mass of sodium sulfate anhydrous is 0.95 g and the centrifugation parameter was 5 oC, 10000 rpm (9917.355 g) for 10 min after experiment; the optimal effects of cloud point extraction were that the type and concentration of surfactant were 60 g/L Triton X-100, the volume of ammonium hydroxidewas 65μL, the mass of n-butyl alcohol and sodium sulfate anhydrous were 0.4 mL and 0.243 g, the equilibration temperature and time 50 oC and 30 min. Then we finished the spiked experiment with the estalished method. The recoveries were 67% ~ 105.7% at three spiked levels of 0.05, 0.1, 0.2 mg/kg, and the relative standard deviations was between 0.93% ~ 8.31%. The results of experiment had good accuracy and precision and were in accord with the requirement of determination of veterinary.(ii) In this research, we established a successful HPLC detection method for the targets, and optimized the mobile phase and wavelength. Then we determinated seven target sulphonamides at 260 nm with Inertsil ODS-3 (150mm×4.6mm, 5μm)equilibrated with mobile phase of acetonitrile (A) and a 0.01 mol/L buffer solution of ammonium acetate (B) in a gradient elution programmed. The result of study showed that the calibration curve had good linearity in the range of 0.02 ~ 5 mg/L with correlation larger than 0.9999. The limits of determination (S/N=3) for the sulphonamides were 2.23 ~ 9.79 mg/kg, which was lower than MRLs of many countries. And at the same time, the seven sulphonamides were well separated and avoided the interference of impurity, and the peak of sulphonamides were symmetrical.(iii) The proposed method was easier and faster to perform, had lower limits of quantification and good recoveries, processed prosperities of efficiency and sensitivity, and not consumed organic solvents in the process of preconcentration. It could meet the demands of practical use for the rapid determination of sulphonamides in milk and could decrease the danger to environment and human health.
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