Simple Purification and Ultrahigh-Pressure Liquid Chromatography-Tandem Mass Spectrometry Determination of Five Quinoxaline 1,4-dioxides and their Metabolites in Swine Liver

In some countries, quinoxaline 1,4-dioxide (QdNO) has been banned as a feed additive because of its potential genotoxicity. To assess the residue levels in animal tissues, an ultrahigh-pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed to determine five QdNOs and its eight main metabolites in swine liver. The samples were simply extracted by 0.1% formic acid in acetonitrile (4+6, v/v) after being acidified with 3 mol/L of 0.1% hydrochloric acid, and purified using a HLB cartridge. The UHPLC-MS/MS provided good linearity to the peak area, with the linear correlation coefficients of over 0.98 within the concentration range of 5-500 mu g/L. The limit of detection (LOD) was 0.30-2.51 mu g/kg, and the limit of quantification (LOQ) was 1.10-8.37 mu g/kg for the 13 target compounds. When the target compounds spiked at 10, 100, and 500 mu g/kg, the recoveries ranged from 79.8 to 96.5%. This method is suitable for the residual determination of real samples.