Determination of cefalonium residue in milk by high performance liquid chromatography-tandem mass spectrometry

An analytical method was developed for the determination of cefalonium in milk by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). A total of 1 g milk was deproteinized by acetonitrile. The supernatant was transferred into a test tube to be blown dry with N-2 at 37 degrees C. Then the residue was dissolved with methanol-0. 1% formic acid in water (3:7, v/v). The sample was determined by HPLC-MS/MS after the purification. The chromatographic separation was achieved on a C-18 column using 0. 1% formic acid in water and acetonitrile as mobile phases with gradient elution. Qualitative and quantitative analyses were achieved by HPLC-MS/MS under positive ionization and multiple reaction monitoring (MRM) mode. Matrix-matched calibration curve was used for the quantification. Good correlation coefficients were obtained (r>0. 999) in the mass concentration range of 2-200 mu g/L. The limit of detection (LOD , S/N >= 3) was 0. 5 mu g/kg in milk, and the limit of quantification (LOQ, S/N >= 10) was 2 mu g/kg. The mean recoveries at the four levels of LOQ, 1/2MRL (maximum residue level) , MRL , 2MRL were between 78. 5% and 86. 2%, with the intra-day relative standard deviations (RSDs) of 1. 5% to 6. 2% and inter-day RSDs of 2. 9% to 5. 6%. In conclusion, the established method can be applied for the determination of cefalonium residue in milk.