Determination Of Six Zeranols Residues In Milk And Dairy Products

Milk and dairy products are the best foods that provide people with nutrients such as protein,vitamins and calcium.They are often contaminated with mycotoxins during storage and processing.Zeranols?ZERs?can enter the milk through the blood-milk barrier,resulting in the presence of ZERs in milk and dairy products and accumulating in the body.About the residue standard of ZERs in food,many countries have formulated strict regulations.In the announcement No.235 of the Ministry of Agriculture of China,zearalanol cannot be detected in edible animal tissues.In order to effectively supervise the quality of milk and dairy products,it is of great significance to establish a reliable,accurate and sensitive ZERs residue detection and analysis method.In this paper,the purification of QuEChERS was studied.A method for the determination of ZERs in milk,cheese and milk powder by high performance liquid chromatography-tandem mass spectrometry?HPLC-MS/MS?was developed.The main contents of the study are as follows:1.A method for simultaneous determination of six zeranols residues in milk was developed by HPLC-MS/MS.The extraction solvent was optimized and the extraction times were repeated.The matrix was purified by QuEChERS method and separated on ZORBAX SB-C₁₈ column using acetonitrile-ammonium acetate water as mobile phase.The results showed that the good linearity was obtained for the ZERs at the concentration of 0.1–50?g/L with the linear correlation coefficients more than 0.995.The limits of detection and the limits of quantification for zeranols were 0.05–0.1?g/kg and 0.25–0.5?g/kg,respectively.The recoveries at three concentration levels were in the range of91.8%–114.5%.The repeatability expressed as relative standard deviations was ranged from 3.2%to 14.4%.2.A method for simultaneous determination of 6 zeranols residues in cheese was developed by HPLC-MS/MS with ceramic homogenizer extracting and QuEChERS purifying.The cheese sample was extracted oscillation by ceramic homogenizer and 1%acetonitrile acetate?v/v?.After cleaning up with C₁₈ and PSA.Then re-dissolved solution was separated on a ZORBAX SB-C₁₈ column with gradient elution using 5 mmol/L ammonium acetate and acetonitrile.The cheese sample was analyzed under the multiple reaction monitoring mode with negative electrospray ionization and quantified by matrix matched calibration curve.The linearities for the zeranols were 0.5-50?g/L with the linear correlation coefficients more than 0.998.The limits of detection and the limits of quantification for zeranols were 0.5?g/kg and 1?g/kg,respectively.The recoveries at three spike levels were in the range of 76.6%-112.3%.The repeatability expressed as relative standard deviations was ranged from 2.5%to 14.5%.3.By optimizing the method,a method for simultaneous determination of six zeranols residues in milk powder was developed by HPLC-MS/MS with QuEChERS.The sample was diluted with deionized water,extracted by 1%acetonitrile acetate and sodium acetate salting out,cleaned up with C₁₈,PSA and Magnesium sulfate anhydrous.The analytes were separated by a reversed phase C₁₈ column and gradiently eluted with5 mmol/L ammonium acetate and acetonitrile.The milk sample was analyzed under the multiple reaction monitoring?MRM?mode with negative electrospray ionization?ESI-?and quantify by internal standard method.The good linearity was obtained for the six zeranols at the concentration of 0.1-50?g/L with the linear correlation coefficients more than 0.999.The limits of detection?LOD?and the limits of quantification?LOQ?for zeranols were 0.1?g/kg and 0.2?g/kg,respectively.The recoveries at three concentration levels were in the range of 85.2%-119.3%.The repeatability expressed as relative standard deviations?RSD?was ranged from 0.3%to 12.2%.In summary,through the detection of ZERs in milk and dairy products and the verification of recovery and correlation coefficient,it was found that this method has the characteristics of simple operation,high sensitivity and good reproducibility,and was suitable for the detection and monitoring of ZERs in milk and dairy products.