GC-MS Determination of Residual Acetanilide Herbicides in Cereals After Purification with Gel Permeation Chromatography and Solid-phase Extraction

A method for determination of residual amounts of 11 acetanilide herbicides in cereals by GC-MS was proposed.It was reported that samples of rice,corn and wheat were extracted with mixed solvent of acetone and n-hexane (1+2),but sample of soybean should be extracted with acetonitrile.The extracts obtained should be purified to remove the fatty acids carried over from the matrixes of cereals in order to eliminate matrix interferences on the determination of the herbicides.As shown by the results of study,the Florisil SPE columns was quite efficient for purification of the extracts of rice,soybean and wheat samples,and the gel permeation chromatography (GPC) should be used for corn.The Bio-Beads S-X3 GPC column was used for the purification of corn extract and the mixed solvent of cyclohexane and ethyl acetate (1+1) was used as mobile phase in the proposed method.Qualitative detections were made on the base of ratios of retention time and abundance of characteristic ions,while quantitative analysis was performed on the base of values of intensity of the characteristic ions.Detection limits (3S/N) found for the 11 herbicides were in the range of 0.01-0.02 mg·L-1.Recovery and precision of the method were tested at 3 concentration levels,giving results of recovery in the range of 72.8% to 110.2%,and RSD′s (n=5) less than 10%.