Abstract: An analytical method for the determination of fenbutatin oxide (FBT) residue in oranges by capillary gas chromatography-flame photometric detection (GC-FPD) was developed. The FBT was extracted with acetone-acetic acid (99:1, v/v) and hexane, filtered and evaporated by nitrogen evaporator in a water bath at 35 ℃. The residue was dissolved in hexane. The FBT in the solvent was derivatized with ethyl magnesium bromide for 15 min, 1 mol/L hydrochloride was added, the supernatant was collected and the solvent was evaporated to get dry supernatants, then the supernatant was dissolved in hexane and cleaned up with a silica solid phase extraction column, eluted with 5 mL hexane-dichloromethane (4:1, v/v), determined by GC. The standard curve was linear in the range of 0.2~2.0 mg/L. The correlation coefficients (r) were more than 0.9995, the average recoveries were 79.6%~109.6% with the relative standard deviations (RSDs) of 3.60%~9.04% at the spiked levels of 0.1~0.4 mg/kg, and the detection limit of fenbutatin oxide was 0.1 mg/kg. This method is suitable for the analysis of fenbutatin oxide residue in orange products.

Key words: fenbutatin oxide (FBT), orange , residue, gas chromatography (GC)