USE OF AN MFO-DIRECTED TOXICITY IDENTIFICATION EVALUATION TO ISOLATE AND CHARACTERIZE BIOACTIVE IMPURITIES FROM A LAMPRICIDE FORMULATION

Recently, a field formulation of the lampricide containing 3-trifluoro methyl-4-nitrophenol (TFM) was identified as a potent inducer of mixed -function oxygenase (MFO) detoxification enzymes in fish. It was furth er shown that induction was not associated with primary formulation in gredients. Using a toxicity identification evaluation (TIE) approach b ased on rainbow trout hepatic MFO activity, the TFM field formulation was investigated to isolate the compound(s) responsible for induction. Solid phase extraction and reverse-phase high-pressure liquid chromat ography (HPLC) isolated activity in two distinct fractions, which were profiled by gas chromatography-high-resolution mass spectrometry. The major constituents in both fractions were confirmed by synthesis as n itro-, trifluoromethyl-, and/or chloro-substituted diphenyl ethers. Ho wever, fish exposures to the pure compounds failed to cause MFO induct ion. After further fractionations by HPLC, induction was determined in three new subfractions. Confident identification of a chloro-nitro-tr ifluoromethyl-substituted dibenzo-p-dioxin has been made in two of the se fractions. Although the specific chemicals responsible for inductio n have not been confirmed, a suite of impurities including chloro-, an d/or nitro-, and/or trifluoromethyl-substituted phenols, diphenyl ethe rs, and dibenzo-p-dioxins have been identified in the formulation. It is likely that these materials originate during industrial synthesis o f TFM. These findings suggest that additional structurally related imp urities are also present in this formulation.