DETERMINATION OF HERBICIDE RESIDUES IN SOIL IN THE PRESENCE OF PERSISTENT ORGANOCHLORINE INSECTICIDES

A rapid and reproducible gas-chromatographic method has been developed for determination of residues in soil of some widely used herbicides such as trifluralin, metribuzin, alachlor, acetochlor, metolachlor, pendimethalin, simazine, atrazine, prometryne, in the presence of persistent organochlorine insecticides (p,p-DDT, o,p-DDT, p,p-DDE, alpha-HCH, gamma-HCH, heptachlor). Determination of some herbicides by GC/ECD is difficult since their relative retention times on packed columns usually used for pesticide analysis are equal or close to those of some persistent organochlorine insecticides which can still be found almost everywhere, especially in cultivated soils. A 1.8 m column of 3% OV-225 + 5% SE-52 in a ratio of 1.4:0.9 gave good separation of all herbicides and insecticides mentioned. The influence of 6 solvents and solvent systems applied most frequently for soil extraction of pesticide residues on recovery of the compounds under study was examined. Acetonitrile was the most suitable extractant as it rendered highest residue recoveries and minimal amount of co-extractives. Residues of simazine, atrazine, and prometryne were determined in the same extracts by the use of NP-detector and a column of 5% Carbowax 20 M. Recoveries of the compounds under study were in the interval of 86-103% without cleanup and 78-94% when cleanup was carriet out. The method can be used in pesticide monitoring of soil as it offers an opportunity for rapid determination of soil applied herbicides and persistent organochlorine insecticides which are some of the most common pollutants in cultivated soils.