Determination of amperozide residues in swine liver using liquid chromatography-mass spectrometry.

Amperozide 4-[4,4-bis(4-fluorophenyl)butyl]-N-ethylpiperazine-1- carboxamide) is used in veterinary medicine because of its sedative effect on pigs. A method developed for the detection of amperozide residues in porcine liver using liquid chromatography with thermospray mass spectrometry (LC-MS) is described and compared with LC with electrochemical detection (LC-ED). For LC-ED analysis, the samples were extracted with acetonitrile and cleaned up on a Sep-Pak C18 cartridge. The residues of amperozide were separated on a C8 polymer-based reversed-phase column and determined by using amperometric detection at +1050 mV. For LC-MS analysis, the samples were extracted with ethanol and cleaned using liquid-liquid extraction. After separation on a C8 polymer-based reversed-phase column, the residues were detected by discharge-assisted ionization with positive ion detection MS using single-ion monitoring. The positive discharge ionization produced typical [M+H]+ molecular ions of amperozide (m/z 403) and the internal standard (m/z 431). The limit of quantification for both methods, determined by using spiked blank liver in the concentration range 20-100 micrograms kg-1, was found to be below 70 micrograms kg-1.