SPE-GC-MS DETERMINATION OF RESIDUAL GIBBERELLIN IN FRUITS

The fruit sample is crashed and extracted twice with acetone-H2O(5+1) mixture under low temperature.Acetone in the extract is removed by distillation at 30 ℃ under reduced pressure.The distillate obtained is filtered on a 0.45 μm PTFE membrane.The solution at pH 2.5±0.02 is then purified on C18 solid phase extraction column,by passing through the column at a flow-rate of 5 mL·min-1.After suction for 5 min to remove the liquid from the column,the object compound on the column is eluted with 5 mL of methanol,which is collected and an aliquot of 1 μL is taken for the GC-MS determination.The retention behavior of gibberellin on the C18 extraction column was studied and optimized.As compared with the liquid phase extraction,the sample was more effectively purified by the solid-phase extraction.No interfering peaks were observed near by the peak of gibberellin.By the use of HP-1 capillary column in GC and the application of selected ion mode in MS,the matrix interferences of different kinds of fruit samples from various origins were overcome,and higher sensitivity of determination was obtained than the fullscanning detection method.Linearity of determination of the present method is in the range from 0.11 mg·L-1 to 3.3×103mg·L-1,with a detection limit of 0.11 mg·kg-1.Recoveries obtained were in the range of 75.3% to 101.3%.RSDs found were less than 4.75%.