Abstract: A novel method was developed for the determination of levamisole in animal livers by liquid-liquid extraction and gas chromatography-mass spectrometry. Levamisole hydrochloride was transferred to levamisole in alkaline solution, and then extracted into ethyl acetate. Two liquid-liquid extraction steps were carried out with HCl aqueous solution and potassium hydroxide-dichloromethane system in turn, and the liposoluble substances and the water-soluble substances were removed, respectively. The qualitative and quantitative analyses of levamisole were achieved by gas chromatography-mass spectrometry (GC-MS) system. The characteristic fragments m/z 148, 176 and 204 were selected and m/z 204 was used as the quantitative ion. A good linear relationship was obtained between the peak area and the mass concentration of levamisole from 0.25 mg/L to 3.0 mg/L with the correlation coefficient of 0.999. The limit of quantitation (LOQ) for levamisole was 5 μg/kg, which was much lower than the international maximum residue limit. The average recoveries of levamisole spiked in chicken liver, duck liver, rabbit liver and pig liver samples at three spiked levels ranged from 76% to 106% with the relative standard deviations less than 9%. The method is simple and stable without tedious sample preparation, and suitable for the determination of levamisole in animal livers.

Key words: animal liver, gas chromatography (GC), levamisole, mass spectrometry (MS), liquid-liquid extraction