Identification of the major metabolites of prochloraz in rainbow trout by liquid chromatography and tandem mass spectrometry

The metabolic pattern of the imidazole fungicide prochloraz [N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl]imidazole-1-carboximide] was investigated in rainbow trout (Oncorhynchus mykiss). Following a single oral administration of [(14)C]prochloraz, levels 4.3 +/- 4.1 and 3.9 +/- 1.8% of the dose were excreted in the bile after 48 h in male and female animals, respectively. Urinary radioactivity accounted for 1.3 +/- 0.4 and 2.4 +/- 1.1% of the dose over the same period in males and females. Metabolites from both matrices were separated by reversed-phase HPLC with radioactive detection and analyzed by positive and/or negative electrospray ionization mass spectrometry. No unchanged prochloraz was detected in the analyzed excreta. The major biotransformation products in bile were the aldehyde corresponding to the cleavage of the imidazole ring, N-2-(2,4,6-trichlorophenoxy)ethylurea, and the glucuronide conjugate of 2,4,6-trichlorophenoxyethanol. In urine, the major metabolite was 2,4,6-trichlorophenoxyacetic acid. On the basis of enzymatic hydrolysis by beta-glucuronidase and LC-MS analyses, this study demonstrates that rainbow trout are able to biotransform prochloraz, mainly as glucuronide conjugates.     

Photochemical degradation of acifluorfen in aqueous solution

To elucidate the photochemical behavior of diphenyl ether herbicides in superficial waters, the photodegradation of acifluorfen, 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzo?c acid (CAS Registry No. 50594-66-6), was studied in water and acetonitrile. All experiments were carried out under laboratory conditions using a solar simulator (xenon arc) or jacket Pyrex reaction cell equipped with a 125 W high-pressure mercury lamp. The calculated polychromatic quantum efficiencies (Phi(solvent)) of acifluorfen in different solvents are as follows (units are degraded molecules photon(-1)): Phi(water) = 10(-4), Phi(acetonitrile) = 10(-4), Phi(methanol) = 10(-4), and Phi(hexane) = 10(-2). The results obtained in this work are in good agreement with the literature value of monochromatic quantum yield. HPLC-MS analysis (APCI and ESI in positive and negative modes) was used to identify acifluorfen photoproducts. These results suggest that the photodegradation of acifluorfen proceeds via a number of reaction pathways: (1) decarboxylation, (2) dehalogenation, (3) substitution of chlorine group by hydroxyl or hydrogen groups, and (4) cleavage of ether linkage, giving phenols. Photorearrangement products were studied by other investigators. No such products were observed. In addition, it was found that the trifluoro functional group on acifluorfen was not affected by any transformation, and no products of a nitro group reduction were found.