Evaluation of ractopamine cross-reactivity in several commercially available beta-agonist enzyme immunoassay kits.

Several enzyme immunoassay test kits are commercially available for screening of matrices including cattle feed, tissues, faeces and urine for the presence of beta-agonists. The kits utilized for this evaluation offer sensitivity as low as 0.1 ng ml-1 (assay solution concentration, not test sample). Evaluation of ractopamine hydrochloride (LY31537) solutions at concentrations as high as 1000 ng ml-1, using six different kits from four different manufacturers, showed cross-reactivity of less than 0.5%.