Foam-Charcoal Chromatography for Analysis of Polychlorinated Dibenzodioxins in Herbicide Orange

Abstract

Abstract Herbicide Orange (HO) is a mixture of n-butyl esters of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). The 2,4,5-T is known to contain 2,3, 7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and other chlorinated aromatic contaminants. Adsorption of TCDD from HO on small amounts of powdered charcoal results in sample cleanup adequate for electron capture gas-liquid chromatographic (GLC) analysis. Column flow restrictions with powdered charcoal are overcome by using polyurethane foams as a dispersive support, HO is dissolved in chloroform and percolated through a column containing a mixture of PX-21 activated carbon suspended on clean polyurethane foam (14.9% charcoal/ 85.1% foam, w/w). Subsequently, the column is washed with benzene, and TCDD is recovered with toluene-benzene (1+1). Samples containing less than 1 μg TCDD/ml required additional sample cleanup on activated alumina prior to GLC analysis. The average recovery of TCDD determined from 4 replicate radiometric measurements was 91.4% (standard error = 4.0). TCDD residues greater than 0.02 μg/ml in HO samples were quantitated by electron capture GLC after cleanup. The presence of TCDD and pentachlorodibenzo-p-dioxin was confirmed by GLC-mass spectroscopy. In addition, tetrachloro- and pentachlorodibenzofurans were inferred by GLC-mass spectrometry.