Veterinary Drugs Residue Methods


 



Category Anticoccidials, including nitroimidazoles
Drug Class Name Monensin, Ionophore coccidiostat
Method Title Monensin
Method Date 1991/07/01
Method Type Screening
Scope and Application The method is applicabile for screening the presence of Monensin.
Method Summary Homogenized lean liver/kidney tissue in methanol is extracted by centrifugation and the supernate further extracted with carbon tetrachloride which is then evaporated to dryness. This residue is further extracted in hexane to remove fat and the hexane evaporated. The final residue is re-dissolved in methanol. In case of fat interference in liver extracts, clean-up may be done using silica gel columns. Here, monensin is eluted from the column with chloroform: methanol (95/5, v/v) and after evaporating the eluate, the final residue is dissolved methanol. Ground fat tissue is extracted in methanol by centrifugation and the supernate evaporated to dryness prior to clean-up on a silica gel column. Monensin is eluted from the column with chloroform: methanol (95/5, v/v) and after evaporating the eluate, the final residue is dissolved methanol. Analysis is done on thin layer chromatography (TLC) by a bioautographic technique using Bacillus subtilis. A mixture of carbon tetrachloride, benzene, ethylene glycol monomethyl ether is used as the TLC developing solvent. The plate is air-dried and fixed by spraying the surface with melted agar using an atomizer-type sprayer attached to laboratory compressed air supply. The plate is equilibrated to room temperature and additional melted agar (seeded agar) inoculated with a B. subtilis inoculum is poured onto the TLC plate. The plate is allowed to cool until the agar sets. The plate (bioautograph) is incubated overnight and then sprayed with a solution of 2-p-iodophenyl-3-p-nitrophenyl-5-phenyl tetrazolium chloride after incubation. Monensin zones may be located on the bioautograph and the monensin concentration estimated by visually comparing zone sizes from experimental samples to zone sizes from standard recovery samples.
Applicable Concentration Range
QC Requirements See attached SOP
Method Source USDA-FSIS
Method SOP PDF icon SOP 
Citation