Nitroimidazoles are a class of veterinary drugs used for the treatment and prevention of certain bacterial and protozoal diseases in poultry, swine dysentery and genital trichomoniasis in cattle. Since the safety assessment of nitroimidazoles showed them to be genotoxic, carcinogenic and mutagenic, a number of nitroimidazoles have been banned for therapeutic purposes in different countries. Moreover, nitroimidazoles have also been extensively used as growth promoters in food-producing animals. Due to their efficacious improvement in meat production and feed conversion, deliberate use still exists. Therefore, the illegal use of nitroimidazoles in animal husbandry must be monitored. A sensitive method based on LC-MS/MS for the simultaneous determination and confirmation of five banned nitroimidazole drugs including metronidazole, ronidazole, dimetridazole, metronidazole-OH (metabolite of metronidazole), and 2-hydroxymethyl-1-methyl-5-nitroimidazole (metabolite of ronidazole and dimetridazole) in bovine muscle, using ronidazole-d3 as an internal standard, was developed and validated. After extraction with ethyl acetate and evaporation, the nitroimidazoles were reconstituted in petroleum ether and purified, and LC-MS/MS analysis was performed. The method was validated according to Brazilian Regulation 24/2009 (equivalent to European Union Decision 2002/657/EC). Parameters such as decision limit (CCα), detection capability (CCβ), precision, accuracy, uncertaincy and ruggedness were determined. Average accuracy of the five nitroimidazoles from bovine muscle fortified at 5 levels (0.5, 1.0, 1.5, 2.0 and 2.5 μg kg(-1)) ranged from 96% to 103%. The calculated CCα ranged from 0.0 to 0.17 μg kg(-1); CCβ ranged from 0.08 to 0.41 μg kg(-1). A complete statistical analysis was performed and the results indicate that the method is robust when subjected to day-to-day analytical variations.

Boldenone, an androgenic steroid, is forbidden for use in meat production in most countries worldwide. Residues of this drug in food present a potential risk to consumers. A sensitive LC/MS/MS method for analysis of 17β-boldenone using boldenone-d3 as an internal standard was developed. An enzymatic hydrolysis and extraction using ethyl acetate, methanol, and hexane were performed in the sample preparation. Parameters such as decision limit (CCα), detection capability (CCβ), precision, recovery, and ruggedness were evaluated according to the Brazilian Regulation 24/2009 (equivalent to European Union Decision 2002/657/EC) and International Organization for Standardization/International Electrotechnical Commission 17025:2005. CCα and CCβ were determined to be 0.17 and 0.29 μg/kg, respectively. Average recoveries from bovine liver samples fortified with 1, 1.5, and 2 μg/kg were around 100%. A complete statistical analysis was performed on the results obtained, including an estimation of the method uncertainty. The method is considered robust after being subjected to day-to-day analytical variations and has been used as a standard method in Brazil to report boldenone levels in bovine liver.

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