Comparison of two post-column derivatization systems for HPLC determination of aflatoxins in Citri Reticulatae Pericarpium

Objective: To evaluate two post-column derivatization systems(derivatization with iodine,and with electrochemically generated bromine) for HPLC determination of aflatoxins in Citri Reticulatae Pericarpium.Methods: The samples were cleaned up on immunoaffinity columns and analyzed by HPLC with post-column derivatization and fluorescence detection.For chromatographic separation,a Diamonsil ODS C18(5 μm,4.6 mm × 200 mm) column was employed.The detection was observed by fluorescence with the excitation wavelength at 360 nm and the emission wavelength at 450 nm.For the post-column derivatization system with iodine(I2),the separation was carried out on the mobile phase of methanol-acetonitrile-water(25∶ 18∶ 57) with a flow rate of 0.8 mL.min-1,the iodine 0.05% solution was used as the derivatization reagent which was delivered at a flow rate of 0.3 mL.min-1 and the reaction coil was maintained at 70 ℃.For derivatization with electrochemically generated bromine(KOBRA),the mobile phase consisted of a mixture of methanol-acetonitrile-water(20∶ 20∶ 60) with a flow rate of 1.0 mL.min-1.To each liter of the mobile phase was added 120 mg potassium bromide and 350 μL of 4 mol.L-1 nitric acid.Results: Good linear relationships were obtained within the ranges of 1.2-36 pg for aflatoxin G2 and B2,and 2-120 pg for aflatox in G1 and B1,respectively,r 0.9997.The recoveries were between 60%-101%.Conclusion: The results of two post-column derivatization systems are equivalent.However,KOBRA has higher sensitivity,easier operating procedure,and less analytical time,and it is also applicable to the determination of aflatoxins in Citri Reticulatae Pericarpium.