Detection of Monensin Residues in Poultry Liver Using an Enzyme Immunoassay

Abstract

Monensin, a carboxylic acid ionophore, is commonly fed to poultry to control coccidiosis. A method for the detection and quantification of monensin residues in liver has been developed. Samples (3 g) were extracted with acetonitrile–water and applied to a competitive enzyme immunoassay using a polyclonal antiserum raised against a monensin–transferrin conjugate. The limit of detection (mean + 3s) calculated from the analysis of 12 known negative samples was 2.91 ng g ^{- 1} . Intra- and inter-assay RSD were determined as 8.5 and 10.6%, respectively, using a liver sample fortified with 20 ng g ^{- 1} monensin. A pharmacokinetic study in which 70 six week old broilers were fed monensin at a rate of 120 mg kg ^{- 1} in their feed for 14 d resulted in mean monensin liver residues of 102 ng g ^{- 1} . However these had fallen below the limit of detection of the assay within the 3 d withdrawal period recommended by the manufacturer.