Optimization of hydroponic bioassay for herbicide tepraloxydim by using water free from chlorine
2003
Sandín España, Pilar | Llanos, S. | Magrans, J. O. | Alonso Prados, José Luis | García-Baudín, J. M.
Initial attempts to develop a hydroponic bioassay test for tepraloxydim failed due to lack of repeatability. Investigation of the fate of tepraloxydim in test media revealed that small residues of chlorine and chloramines present on distilled water cause fast degradation of the herbicide. Half-life of tepraloxydim in the presence of a chlorine excess was determined to be DT 50 < 5 s. Reaction with chloramines was slower (DT50 = 4.5 h). Finally, when this factor was eliminated by using water completely free of chlorine, the main process that took place was the isomerization of the oxime group (E vs. Z). However, the overall degradation was slow (DT 50 = 17 days) and the hydroponic bioassay was optimized in the absence of chlorine.
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