Elucidation of metabolic pathways for pesticides in rotation crops

Recently the Environmental Protection Agency has granted permission to obtain tolerances for pesticide residues in rotation crops. Pesticides applied either pre or postemergence to crops are generally rapidly metabolized in soil to polar and bound residues. These soil residues are usually less available than the applied pesticide for plant uptake. It is a time consuming and difficult task to obtain metabolism data on rotation crops characterized by low uptake. Methidathion, an insecticide for plants, will be used as an example of low uptake by subsequently grown rotation crops. Techniques will be presented to generate large quantities of metabolites utilizing short-term laboratory studies. These metabolites can then be easily identified by the appropriate spectral techniques. Synthesis of standard compounds must be done for comparison to metabolites found in rotation crops. A variety of chromatographic systems will be discussed and evaluated for their suitability for this purpose.