title: [Determination of nine penicillin residues in milk by high-performance liquid chromatography-mass spectrometry].
abstract: OBJECTIVE
  To establish a high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) method for detection of nine penicillin residues in milk.
  
  
  METHODS
  The samples were precipitated with acetonitrile and degreased with n-hexane for pre-processing. The chromatography was performed by reversed-phase HPLC in a C₁₈ column and eluted gradiently on line for 11 min. The mobile phases were water with formic acid (pH 3.1) and acetonitrile-water with formic acid (pH 3.1). By optimizing the mass condition, the method was operated by multiple-reaction monitoring (MRM) and quantitated by external standard calibration.
  
  
  RESULTS
  The standard curves were linear in concentration range of 0.4 approximately 400 μg/L and all nine penicillins showed a good linear relationship in the milk matrix (r>0.990). The detection limit of the method was from 0.1 to 0.8 μg/L while the limit of quantification was from 0.3 to 2.6 μg/L. The average recoveries were higher than 80%. The within-day precisions were less than 8.5%.
  
  
  CONCLUSIONS
  The established method is convenient, rapid and accurate and meets the requirement of monitoring penicillin residues in milk.
authors.affiliation: School of Medicine and Life Sciences, Zhejiang University City College, Hangzhou 310015, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.forename: Gang
authors.initials: G
authors.lastname: Du
authors.forename: Xiang-rong
authors.initials: XR
authors.lastname: Li
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004350:Drug Residues / Q000032:analysis*; D008892:Milk / Q000737:chemistry*; D010406:Penicillins / Q000032:analysis*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D010406:Penicillins