GC-MS Determination of Acetanilide Herbicides in Tobacco After Purification with Gel Permeation Chromatography

A method for determination of residual amounts of 3 acetanilide herbicides, i.e. metolachlor, diphenamide and napropamide, in tobacco by GC-MS was proposed. Samples were extracted with mixed solvent of ethyl acetate and n-hexane (1+1). The extract obtained was purified by gel permeation chromatography using mixed solvent of ethyl acetate and n-hexane (1+1) as mobile phase. The eluates were taken for separation by GC and the contents of 3 acetanilide herbicides were determined by MS under select ion monitoring (SIM) mode. Values of detection limit (3S/N) found were 0.45 ng·g-1 for metolachlor, 0.50 ng·g-1 for diphenamide, and 0.30 ng·g-1 for napropamide. Tests for recovery were made by addition of mixed standard solution at 2 different concentration levels, values of recovery found were in the range of 90.0%-102.0%, with values of RSD′s (n=6) in the range of 2.6%-3.2%.