it is illegally used as a reparti- tioning agentin meat-producing animals 4 6 The use of as a growth promoter in cattle destined for human con sumption is illegal and implies a threat to public health, because several human poisonings have been linked to consumption of meat products contaminated with CLB dues The use of CIB as growth promoter in cattle banned in the European Union 18l Mexico 19-11l, and many other countries. The human effects include increased heart rate blood pressure, anxiety, palpitation, and tremor skeletal muscle f12l. The Codex Alimentarius Commission recommends maximum residue limits (MRIs for cattle 02 ngg in muscle and fat, 6ngg in and kidney, oos ng/ml, for catte milk, expressed as parent drug 13 To analyze residues in animal tissues, should be noted that they are highly complex feature matrices, furthermore the extraction and detection of substances present in con centrations of the or of ng g (ppbl or even less, should performed with high selectivity I4 For food security, the analytical method for determining residues of CIR is indis pensable. There are various methods for determining CLB including immunological techniques such as enzyme linked immunosorbent assay li4 s chromatography coupled with mass spectrometry (GCMS) H6-18, high-performance liquid chromatography (HPLC-UV detection B 1920l liquid chromatography coupled with tandem mass spec- 21 or with mass spectrometry (LC/MS) trometry CMS/MS) Of the reported methods, immunological techniques a the lea used for quantification, although they are fast qual itative screening techniques. GCMS methods involve tedious steps for derivatization of CLB 123l Thus, HPLC was chosen as the technique for and accurate quantification of CLB in bovine liver samples. In the present work, a rapid, accurate, and sensitive method for determining CLB HPLC with UV absorbance detection was optimized with reference to published pro- cedures of the United States Department of Agriculture A simple and time-saving (USDA and Chang et al method for extraction and filtration for direct analysis was used in this experiment. The main objective of this study was to develop optimal conditions for the method, which could be applied to the determination of CLB in bovine liver. This analytical method was then implemented to determine the CIB levels in amples purchased from a meat distribution center in