Improved Extraction of Atrazine and Metolachlor in Field Soil Samples

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Abstract
A method was developed for extraction of weathered residues of atrazine and metolachlor from field soils; soils had last been treated with commercial formulations of the herbicides 8-15 months prior to sample collection. Maximum yields were obtained by batch extraction at 75 °C for 2-16 h with methanol-water (80 + 20) In a sealed vial. Hydrolysis or other decomposition reactions were minor or negligible, depending on the extraction time. This method is an improvement over published methods that are validated by spike recoveries; the proposed method gives 1.7-1.8 times higher yields compared to shaking for 2 h at room temperature, and 1.3-1.8 times higher yields compared to Soxhlet extraction. The reproducibility of the method was better than 12%. The results underscore the Impact of nonequllibrlum sorption of organic compounds on analytical methodology and emphasize the need to validate extraction methods with field samples