A liquid chromatography-electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method was developed for monitoring and detection of four different drugs, namely acetanilide, pentylenetetrazole, phenacetin, and tetramethrin in porcine muscle, pasteurized milk, and table egg samples. For acetanilide and pentylenetetrazole, the samples were extracted with 0.1 % formic acid in acetonitrile, followed by defatting with n-hexane, partitioning at -20 °C for 1 h, centrifugation, and filtration, whereas the quick, easy, cheap, effective, rugged, and safe "QuEChERS" method was used for phenacetin and tetramethrin. The final extracts were combined and analyzed in a single chromatographic run using an XBridge(TM) analytical column and 0.1 % formic acid and 10 mM ammonium formate in ultrapure water (A) and 0.1 % formic acid and 10 mM ammonium formate in methanol (B) as the mobile phase. Owing to the unavailability of internal standards, matrix-matched calibrations were used for analyte quantification with coefficients of determination (R (2)) ≥ 0.9865. The intra- and inter-day accuracies ranged from 60.75 to 90.90 % and from 63.75 to 89.30 %, respectively, while the respective analytical precisions were 1.48-17.44 % (23.3 % for porcine sample spiked with phenacetin) and 1.97-15.78 %. The limits of quantification (LOQ) were between 0.5 and 2.5 ng/g in the matrices tested. Food samples purchased from local markets in Seoul were analyzed using the developed method and none of the tested drugs was detected.
Keywords: Animal food products; Milk; Porcine muscle; QuEChERS; Table eggs; Tandem mass spectrometry; Veterinary drugs.