Determination of Three Nitroimidazole Residues in Royal Jelly by High Performance Liquid Chromatography-Tandem Mass Spectrometry

A method for the analysis of trace metronidazole (MTZ), dimetridazole (DMZ), and ronidazole (RNZ) residues in royal jelly was developed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). After the samples were dissolved in sodium hydroxide solution to disassociate target analytes from the matrix, liquid-liquid extraction methods using ethyl acetate solvent were used. Matrix effects were minimized, and good quantitation results were obtained by using highly-selective reaction monitoring (H-SRM) technology when deuterated dimetridazole (dimetridazole-D3) was selected as the internal standard. Limits of detections (LODs) were 1.0 μg/kg for DMZ and 0.5 μg/kg for MTZ and RNZ (S/N>5). Limits of quantitation (LOQ) were 2.0 μg/kg for DMZ, 1.0 μg/kg for MTZ and RNZ (S/N>10). The linear ranges were 2.0–200 μg/L for all target analytes. Recoveries and relative standard deviations (RSDs) were in the ranges of 96.6%–110.6% and 2.1%–7.4%, respectively. This method is suitable for statutory residue testing in the National Residue Surveillance Plan in China and meets the requirement for export.