Development and Validation of a Multiresidue Method for β-Agonists in Biological Samples and Animal Feed

Abstract

Abstract An analytical strategy for the detection of β-agonlsts containing either an N-tert-butyl or N-sopropyl group is described. Extract purification Is based on Immunoaffinity chromatography; final detection, identification, and determination are by gas chromatography/mass spectrometry. To prepare the immunoaffinity chromatography materials, poly-valent antibodies are raised against clenbuterol and cimaterol. The immunoglobulin G fractions of the corresponding rabbit antlsera are isolated and coupled onto an activated Sepharose™ matrix. The prepared columns gave quantitative recovery for a large number of structurally related β-agonists at the 200 ng level. To quantitate and control falsenegative results, Isotope-labeled internal standards are used. For animal feed and bovine urine, analytical recoveries were close to 100% for all compounds except salbutamol (56 ± 5%). Recoveries from liver were in the range of 60-70% (salbutamol, 40-50%). Limits of detection, based on the corresponding most abundant Ion, were In the range of 0.05-0.2 μg/kg or μg/L. Limits for Identification, based on the simultaneous detection of 4 diagnostic ions, were In the range of 1-2 μg/kg or μg/L. Repeatability and within-laboratory reproducibility, expressed as percent relative standard deviation, were all well below 15%, which fulfills the EC criteria for reference methods. The multiresidue method Is an efficient, cost-effective way to determine Illegal growth-promoting N-terf-butyl and N-Isopropyl phenylethanolamlnes.