Development and validation of an efficient and innovative method for the quantification of multiclass veterinary drugs in milk by using LC–MS/MS analysis

An efficient analytical method for the simultaneous quantification of 27 veterinary drugs from five different classes (benzimidazoles, betalactams, quinolones, sulfonamides and tetracyclines) in bovine milk using a novel extraction procedure (liquid-liquid extraction with fast partition at very low temperature) and liquid chromatography coupled to tandem mass spectrometry is described. The full analytical method was validated according to Brazilian legislation (normative instruction SDA/MAPA 24/2009) and suitable values were achieved for all the parameters evaluated. Hence, the recoveries were within the established ranges (>70%), except for sulfathiazole (67.4% at the 0.5 MRL level) and marbofloxacin and thiabendazole (112.5 and 114.6% respectively, at the 1.0 MRL level). The repeatability and intermediate precision for all the analytes, expressed as relative standard deviations, were lower than 20 and 25%, respectively. The decision limits (CC sub( alpha )), detection capabilities (CC sub( beta )) and expanded uncertainties were also calculated and satisfactory results were obtained. Finally, the method was applied to 15 actual samples and traces of oxytetracycline and sulfamethazine were detected in three of them.