IAC/cELISA detection of monensin elimination from chicken tissues, following oral therapeutic dosing

A specific screening technique was developed for detecting and quantifying the antibiotic, monensin (Mon), present at residue levels in chicken tissues. Mon was extracted from chicken tissues by enzymic hydrolysis, followed by immunoaffinity chromatography (IAC) and quantitative assessment by chemiluminescent ELISA (cELISA). The cELISA had a working range between 0.1 and 10 ng/ml (CV < 5%) with a limit of detection of 0.06 ng/ml (CV < 3%; B0-3SD). The IAC/cELISA process resulted in an analytical limit of detection for chicken tissues of between 0.09 microgram/kg (liver) and 1.99 micrograms/kg (skin). This analytical strategy was used to evaluate the presence and distribution of Mon in the carcasses of groups of chickens (n = 3) fed with a standard therapeutic dose of Mon followed by withdrawal periods of 0, 1, 2, 3 and 26 days. Mon levels in the tissues of these groups was found to be greatest in fatty tissues. Furthermore, residual levels of Mon persisted in all chicken tissues after withdrawal from a diet containing Mon for far longer than the putative fall in plasma levels have previously indicated.