A study of the stability of conjugates of N‐benzoyl‐N‐(3‐chloro‐4‐fluorophenyl)‐DL‐ alanine during extraction from Avena sativa

Extensive metabolism occurred within 24 h of treatment during studies of N ‐benzoyl N ‐(3‐chloro‐4‐fluorophenyl)‐ DL ‐alanine ( I ) in oats. However, marked differences were observed in the apparent pattern of metabolism when different methods of extraction were used. Two major groups of metabolites were found (based on chromatographic behaviour), the first containing mainly the glucose ester of I , and the second containing other sugar conjugates of I . These groups of metabolites and the residual I could be extracted from plants with either aqueous acetone or boiling ethanol to give the same quantitative distribution of metabolites. However, if 80% ethanol was used as extraction solvent, and sodium hydrogen carbonate was used as a leaf wash prior to extraction, dramatic decreases were observed in the concentration of conjugates formed, and large quantities of the ethyl ester of I were also formed. It is concluded that the common experimental practice of using sodium hydrogen carbonate or other alkaline reagents for washing residual herbicides from treated leaves should be avoided, particularly in studies with acidic herbicides.