Determination of Residual Clenbuterol Enantiomers in Swine Urine by High Performance Liquid Chromatography

A method was developed for the determination of residual clenbuterol enantiomers in swine urine by high performance liquid chromatography. A 10-mL sample was extracted with ethyl acetate under basic condition. Then, clenbuterol enantiomers were stripped from the extract using diluted hydrochloric acid to remove the fat. The hydrochloric acid extract was purified by SCX solid phase extraction (SPE) cartridge. The eluent was dried by nitrogen and then dissolved in 200 mu L methanol. The samples were analyzed on a chiral column (Astec CHIOBIOTIC (TM) V) with a mixture of methanol-acetic acid-triethylamine as the mobile phase and quantified with the external standard calibration curve method. The detection wavelength was set at 301 nm. Good linearities were obtained for the two enantiomers at the concentration of 70 - 5000 mu g/L with the linear relative coefficient more than 0.9996. The recoveries for the two enantiomers in urine were 76.3% - 91.5% at the fortified levels of 1.0 - 20.0 mu g/L with the limit of detection of 0.30 mu g/L. The relative standard deviations were less than 7.0%.