ANALYTICAL METHODS FOR THE DETERMINATION IN SOIL OF HERBICIDES USED IN FORESTRY BY GC-NPD AND GC MS/

Analysis of several herbicides used to control weeds in forestry (sima zine, hexazinone, pendimethalin, and thiazopyr) has been performed by GC-NPD and GC/MS. A method based on the extraction of soil samples in small columns has been used for the determination of these compounds i n soil. Acetone/water (90:10) was used for the extraction of all four compounds, and ethyl acetate can be used when the determination of hex azinone is not required. The recoveries through the method were always >80%, and the detection limit was <0.01 ppm for GC-NPD and GC/MS. Soi l samples from experimental fields, taken at different times after tre atment from the plow layer, were analyzed according to this method, an d values similar to those obtained by a conventional method using mech anical shaking extraction were obtained.