Abstract: A high performance liquid chromatography tandem mass spectrometric（HPLC-MS/MS） method was developed for 2，4-D residues in citrus. The samples were extracted with acetonitrile， salted out in acid condition， and then cleaned up by dispersive solid-phase extraction with dispersant sorbent of primary secondary amine（PSA）. The separation of 2，4-D was performed on a XDB-C18（4.6 mm×50 mm， 1.8 μm）column using a mixture of ammonium acetate methanol and water solution as mobile phase. The qualitative and quantitative analysis for the analyte were carried out under the selective reaction monitoring（SRM）mode with negative electrospray ionization. Under the optimal conditions， the calibration curves were linear in the range of 0.05-1.60 ng·mL-1 for 2，4-D，the limit of detection was 0.002 mg·kg-1，and the limit of quantification was 0.008 mg·kg-1. The average spiked recoveries at 0.10 mg·kg-1， 0.20 mg·kg-1 and 0.40 mg·kg-1 addition concentration were between 76.5% and 95.3% with relative standard deviations（RSDs）less than 10%. The proposed method is accurate， sensitive and high-efficient， and applicable for the determination of 2，4-D in citrus.

Key words: 4-D, citrus, high performance liquid chromatography tandem mass spectrometry（HPLC-MS/MS）, dispersive solid-phase extraction