Development an UHPLC-MS/MS Method for Detection of β-Agonist Residues in Milk

beta-Agonists have been abused as the growth-promoting agent in food-producing animals over 20 years. The proof of using illegal drugs in food, which is necessary for a regulatory action, usually requires a high degree of specificity and sensitivity. This paper reported an ultra-high performance liquid chromatography (UHPLC)-ESI/MS/MS method for the confirmation of multi-residues of the 13 beta-agonist compounds in milk. A wide range of analytes related to beta-agonists (brombuterol, cimaterol, clenbuterol, clenpenterol, clorprenaline, hydroxymethylclenbuterol, isoxsuprine, mabuterol, ractopamine, ritodrine, salbutamol, terbutaline, tulobuterol) with similar chemical structures was investigated in order to demonstrate the applicability of our method. This method consists of a two-step extraction and a MCX SPE cleanup. The final extract was separated by UHPLC within 5 min and then injected in an electrospray ionization mass spectrometry for the determination. Using clenbuterol-D9, salbutamol-D3, and ractopamine-D5 as internal standards, and accomplishing with the matrix matched calibration curves to compensate for the matrix effects, the quantitative data showed good linear response within the concentration ranges studied. The detection limits (CC alpha) and detection capabilities (CC beta) of the analytes were found in the range of 0.01-0.16 mu g/L and 0.03-0.21 mu g/L, respectively. Recoveries of the compounds were found from 82.5% to 101% at the spiked level of 0.05-2.5 mu g/L, and the relative standard deviation was within the range of 7.17% and 16.4%. Furthermore, an inter-laboratory study among eight laboratories was conducted to further validate the method, and the results were found satisfactory.