The performance of an immunoaffinity phase for the purification of cattle liver extracts containing clenbuterol or salbutamol is described. The capacities of the immunoaffinity phase were found to be 440 ng of clenbuterol and 270 ng of salbutamol per g solid phase when measured in phosphate‐buffered saline. The phase yielded greater than 75% recovery of clenbuterol from cattle liver extracts fortified at concentrations equivalent to 12 ng g‐1The capacity for salbutamol was found to be markedly affected by buffer type and the presence of sample matrix components in cattle liver extracts. Immunoaffinity‐purified cattle liver extracts were analyzed by high‐performance liquid chromatography with UV and fluorescence detection. The presence of matrix co‐extractives in the purified extracts was the main factor limiting the applicability of this procedure to the determination of these analytes at residue levels. The achievable detection limits were estimated to be more than 5 ng g‐1for both analytes. The behaviour of salbutamol on this immunoaffinity phase was rather more complex than the high capacity value alone indicates. The data reported here suggest that such capacity values, derived under ideal conditions, should be treated with caution unless supported by recovery data determined for real samples. This consideration may be more important for cross‐reacting analytes than for the primary antigen.