3,3',4,4'-Tetrachloroazobenzene and 3,3',4,4'-tetrachloroazoxybenzene in technical grade herbicides: propanil, diuron, linuron, and neburon.

The levels of 3,3',4,4'-tetrachloroazobenzene (TCAB) and 3,3',4,4'-tetrachloroazoxybenzene (TCAOB) were determined by gas chromatography-electron capture detection in 20 samples of 3,4-dichloroaniline-derived herbicides. The concentrations of TCAB in technical grade propanil, diuron, linuron, and neburon from a variety of manufacturers ranged from 0.10 to 28.40 mg/kg. No relevant difference was found between the two different herbicide classes analyzed.