EXTRACTION OF FREE AND BOUND CARBOXYLIC-ACID RESIDUES FROM FIELD SOILS TREATED WITH THE HERBICIDES BENZOYLPROP-ETHYL, DICLOFOP-METHYL, AND FLAMPROP-METHYL

The breakdown of the herbicidal esters benzoylprop-ethyl, diclofop-methyl, and flamprop-methyl was studied in small field plots at three locations in Saskatchewan after two separate growing seasons. Following extraction of soil samples with aqueous acidic acetonitrile, the parent esters and acid hydrolysis products were determined gas chromatographically. Residues of benzoylprop-ethyl and flamprop-methyl, together with their corresponding acids, were recovered from treated soils at all sites both years, whereas no significant amounts of diclofop-methyl (or acid) were observed in any sampled soils. Following extraction with the acidic acetonitrile solvent, the soil residua were reextracted with cold aqueous sodium hydroxide or hot aqueous triethanolamine solutions to release any benzoylprop, diclofop, or flamprop acids held on the soil in a bound form. From these alkaline digestion studies and experiments conducted to compare the extractions of the three herbicidal acids from fortified soils using cold sodium hydroxide and hot triethanolamine as extractants, it was concluded that any such bound residues could only be present in negligible quantities. © 1979, American Chemical Society. All rights reserved.