Simultaneous Determination of 23 Prohibited Drugs in Swine Urine by Liquid Chromatography Tandem Mass Spectrometry

A liquid chromatography. electrospray ionization tandem mass spectrometric (LC-ESI-MS/MS) method was developed for the simultaneous determination of 23 forbidden drugs including beta-agonists, steriods, nitroimidazoles, sedatives etc. in swine urine. The samples were freeze-dried under vacuum and then dissolved with 10% methanol in water containing 0. 1% formic acid, followed by cleanup and enrichment using Anpel MCX solid phase extraction cartridge. Qualitative and quantitative analysis was achieved for the analytes under the multiple reaction monitoring (MRM) mode after the chromatographic separation on a CNW Athena C-18 (150 mm x 2. 1 mm i. d. , 5 mu m) column. Matrix-matched calibration curves with good correlation coefficients (r>0.99) were obtained in the concentration range of 0. 5-100 mu g/L. The limits of detection (LODs) and the limits of qualification (LOQs) for the 23 compounds were in the range of 0. 5-4. 0 mu g/L (S/N > 3) and 1. 0-10 mu g/L (S/N>10), respectively. The mean recoveries at the four spiked levels of 1. 0-50 mu g/L were between 50.2% and 97.9% with the intra. day relative standard deviation (RSD) less than 10% and inter. day RSD less than 18%. The proposed method was successfully used to detect 23 banned drugs in 200 swine urine samples, two of them contained clenbuterol, with the concentrations of 4.45 and 2.16 mu g/L, respectively.