Confirmatory method for the analysis of carbadox and olaquindox in porcine feedingstuffs using LC-electrospray MS-MS

A method is described for the quantitative determination of the two feed additives carbadox and olaquindox in porcine feedingstuffs. The use of these agents in feedingstuffs was prohibited in the European Union as a result of concerns about their toxicity. Regulatory laboratories are required to have suitably validated analytical methods to ensure compliance with the ban. The analytes were extracted from finished feedingstuffs into acetonitrile : chloroform (1 : 1, v/v), and aliquots (1.0 ml) of the extract were dried down under a stream of nitrogen at 65 degrees C. All residues were re-dissolved in HPLC mobile phase containing acetonitrile/water/formic acid. Analysis was based on LC coupled to positive-ion electrospray MS-MS, with daughter ions for carbadox at m/z 231 and 90, and for olaquindox at m/z 212 and 143 being monitored. The method was validated by analysing feed samples fortified with carbadox and olaquindox at 0.5, 2.5 and 5 mg kg(-1) on three separate occasions. Sample preparation was simple, thus allowing the confirmation of these compounds in large numbers of samples.