title: Rapid forensic selected reaction monitoring liquid chromatography/mass spectrometry determination of ionophore antibiotics found at toxic levels in animal feeds.
abstract: A rapid, accurate, and selective method was developed for the forensic determination of ionophore antibiotics in animal feeds. A simple extraction procedure and liquid chromatography/tandem mass spectrometry (LC/MS/MS) in the selected reaction monitoring (SRM) mode were used for rapid identification and confirmation of monensin and lasalocid in feed samples and for quantitation of monensin. Extracts from a homogenous portion of ground feeds were prepared using liquid-solid extraction and liquid-liquid extraction techniques. Feed extracts were further purified by a simple defatting and solvent wash step and then concentrated to dryness. Feed extract residues were reconstituted in 1 mL LC mobile phase and a 2 microL aliquot injected into the SRM LC/MS system. The latter system used a C18, 100 x 2.0 mm, LC column coupled to a PE-Sciex API 2000 tandem triple quadrupole mass spectrometer equipped with a TurbolonSpray LC/MS interface. Feed samples were extracted and analyzed for the determination of monensin and lasalocid within a couple of hours. Control feed samples fortified with monensin at concentrations from 50 ppb to 5 ppm provided a linear response and calibration curve across this range with a correlation coefficient of 0.996.
authors.affiliation: Cornell University, Analytical Toxicology, College of Veterinary Medicine, 927 Warren Dr, Ithaca, NY 14850, USA. jge2@cornell.edu
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Ebel
authors.forename: Timothy
authors.initials: T
authors.lastname: Wachs
authors.forename: Jack D
authors.initials: JD
authors.lastname: Henion
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis* / Q000506:poisoning; D002138:Calibration; D002417:Cattle; D002853:Chromatography, Liquid; D005506:Food Contamination; D005554:Forensic Medicine; D006736:Horses; D007202:Indicators and Reagents; D007476:Ionophores / Q000032:analysis* / Q000506:poisoning; D007832:Lasalocid / Q000032:analysis / Q000506:poisoning; D013058:Mass Spectrometry; D008985:Monensin / Q000032:analysis / Q000506:poisoning; D012015:Reference Standards; D015203:Reproducibility of Results
chemical_list: D000900:Anti-Bacterial Agents; D007202:Indicators and Reagents; D007476:Ionophores; D008985:Monensin; D007832:Lasalocid