PRECONCENTRATION OF HYDROPHILIC AND HYDROPHOBIC PESTICIDES FROM AQUEOUS-SOLUTIONS AND EXTRACTION OF RESIDUES USING THE POLYMERIC SORBENT WOFATIT-Y77 .2. EXTENSION OF THE STUDIES TO HYDROPHOBIC PESTICIDES - AQUEOUS EXTRACTION OF PESTICIDES FROM PLANT-MATERIAL AND SOIL

Preconcentration of hydrophilic pesticides has been reported (Fresenius Z. Anal. Chem. 1987, 328:484-486) of the insecticides methamidophos, trichlorfon, dimethoate and the herbicides Na-trichloroacetate, fenuron, propachlor and 2,4-D. Meanwhile, the following compounds have been included into the experiments: dimethoxon, methylparathion, bromophos, DDT, bromuron and lenacil from water in the concentration range between 0.05-mu-g/l and 1.0 mg/l; dimethoate and methamidophos from fruits and vegetables in the range of 0.1 mg/kg and dimethoate, propachlor and 2,4-D and a series of triazine, carbamate and urea herbicides from soils in the range of 0.2 to 1.0 mg/kg. The adsorption of dissociated compounds by Wofatit Y 77, depending on the pH intervals investigated, was effective for some compounds, but ineffective for ethephon, glyphosate, CCC and amitrole. Extraction of plant material using NaCl solution yielded recoveries of 65-95% of dimethoate, but for methamidophos bound residues causing reduced recoveries have been observed. Optimal recoveries have been attained for extracting soils and sediments by mixtures of methanol or acetone with water. Studies were performed by using radiolabelled compounds and TLC, whereas GC was effective for selected samples only, depending also on the type of detector used, what has to be studied in further experiments.