Abstract: A method for simultaneous determination of six zeranols residues in milk was developed by quick, easy cheap, effective, rugged and safe (QuEChERS) extraction coupled to high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was extracted with 1% acetate acetonitrile. The extract was degreased with acetonitrile-saturated n-hexane, cleaned up with a mixture of C18, primary secondary amine (PSA) and magnesium sulfate anhydrous. The analytes were separated on a reversed phase C18 column and gradiently eluted with 5 mmol/L ammonium acetate and acetonitrile. These analytes were analyzed under the multiple reaction monitoring (MRM) mode with negative electrospray ionization (ESI-) and quantified by matrix-matched external standard method. Good linearity was obtained for the six zeranols in the concentration range of 0.1–50 μg/L with correlation coefficients of more than 0.995. The limits of detection (LODs) and the limits of quantification (LOQs) for the zeranols were 0.05–0.1 and 0.25–0.5 μg/kg, respectively. The recoveries at three spiked concentration levels were in the range of 91.8%–114.5%. The repeatability expressed as relative standard deviation (RSD) ranged from 3.2% to 14.4% (n = 6).

Key words: zeranols, QuEChERS, high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), milk