Simultaneous determination of salbutamol, ractopamine, and clenbuterol in animal feeds by SPE and LC-MS.

A liquid chromatography-mass spectrometry (LC-MS) method for the simultaneous determination of salbutamol, ractopamine, and clenbuterol in commercial feeds was developed. Samples were extracted with phosphoric acid-methanol solution, and further clean-up was achieved with a C18 cation exchange mixed mode cartridge. Separation of analytes was developed on a C18 column with 0.01 M aqueous ammonium formate solution (pH 3.8)-acetonitrile by gradient program, and characterized by LC-MS on a quadrupole detector, in electrospray positive ion mode. This method provides average recoveries for salbutamol, ractopamine, and clenbuterol of 83-110% and coefficients of variation of 1.5-11% in feeds spiked in the range of 0.5-500 mg/kg. The limits of detection and quantification in feeds were 0.01 mg/kg and 0.05 mg/kg, respectively. Such limits are well below the dose of 2-25 mg/kg feed proposed as effective.