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Partial degradation of 12 selected analytical grade pesticides was produced by heating the chemicals at temperatures between 100 and 400C. Each pesticide was modified physically and chemically at a temperature at least 300–450C below its complete combustion temperature. At these relatively low temperatures eight of the original nine solids (zineb, picloram, dieldrin, atrazine, bromacil, carbaryl, DNBP, and 2,4‐D) remained solid, while dicamba was converted to a liquid. The three liquids (DBCP, vernolate, and malathion) were all converted to solids. Eight of the original 12 compounds also yielded gray to brown to black residues upon heating. Infrared spectroscopic analyses indicated that the extent of degradation of the heated pesticides ranged from formation of a single degradation product to production of a mixture of compounds. Most pesticides, however, were degraded through loss of one or two substituents of the molecule by processes such as dehalogenation and decarboxylation.

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