An analytical method for detecting TCDD (dioxin): levels of TCDD in samples from Vietnam.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an extraordinarily toxic substance that is produced as an unwanted side product in the industrial synthesis of 2,4,5-trichlorophenol, an intermediate in the manufacture of the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) (1, 2). Because of its chemical stability and its lipophilic nature, the possibility exists that TCDD released into the environment could accumulate in food chains. A direct test of the possibility of biologically significant accumulation in animal tissues requires an analytical method able to detect TCDD at levels well below those known to be toxic. The lowest value known for the lethal dose of TCDD is that observed in the guinea pig, for which the single oral dose LD50 is 600 parts per trillion (ppt) body weight (3). Allowing for sublethal toxic effects and providing for a conservative margin of safety, it seems desirable to have an analytical sensitivity of at least 1 ppt. For a 1-g sample this means the method must have a sensitivity of. about 10-12g or 1 picogram (pg). The most common method for analyzing chlorinated organic compounds in tissue samples is gas-liquid chromatography (GLC) with an electron capture detector. Its limit