Detection and identification of substituted phenols as intermediates of concurrent bacterial degradation of the phenoxy herbicides MCPP and 2,4-D.

The concurrent bacterial degradation of 2-(2-methyl-4-chlorophenoxy)propionic acid and 2,4-dichlorophenoxyacetic acid was studied using a stirred tank reactor and a bacterial culture which had been originally derived by enrichment with MCPP. High pressure liquid chromatographic methodology was used to measure both herbicides and it also resolved the corresponding phenols as intermediates, i.e., 2-methyl-4-chlorophenol and 2,4-dichlorophenol. Gas chromatography-mass spectrometry was used to verify the intermediates. UV scans of spent cultures showed that the wave-length of maximum absorption shifted from 282 nm to 280 nm toward the end of incubation, but the characteristic peaks of maximum absorption of these compounds could not be used resolved because of the overlap.