Environmental Toxicology and Chemistry 2002-03-01

Photodechlorination of 3,3'-dichlorobenzidine in water.

Marianne C Nyman, Ken S Haber, Hilkka I Kenttämaa, Ernest R Blatchley

Index: Environ. Toxicol. Chem. 21(3) , 500-6, (2002)

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Abstract

Laboratory experiments have been conducted to elucidate the photochemical behavior of 3,3'-dichlorobenzidine (DCB) and its congeners in aquatic systems. Photodechlorination of DCB was observed in aqueous samples that were irradiated with monochromatic radiation from a variable-wavelength laser at several wavelengths in the range 300 nm < or = lambda < or = 360 nm. Analytical measurements performed by high-performance liquid chromatography (HPLC) and Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry revealed that 3-chlorobenzidine (MCB) was produced as a transient intermediate in the photodechlorination process, with subsequent photodechlorination to yield benzidine as a stable photoproduct. Data obtained from these measurements also suggest the existence of other (unidentified) reaction pathways and products. The time-course measurements of chlorobenzidine congener concentrations and irradiance history were combined with a simple reaction model to develop estimates of reaction kinetics. Model predictions were consistent with results obtained for all wavelengths investigated.