Chromatographic Approach to Environmental Sciences of Dioxin

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Various chromatographic separation media, including alkylated silica packed in quartz tubing, restricted-access reversed-phase packing material, polynuclear aromatic hydrocarbon (PAH) -immobilized silica, and polymeric pseudo-stationary phase for electrokinetic chromatography (EKC), were developed in Kyoto Institute of Technology and Himeji Institute of Technology in cooperation with Copernicus University and Lund University. These materials were applied for the following studies, (1) photo-decomposition of polychlorodioxins and PCBs, (2) sample treatment of serum for GC/MS analysis of dioxins, PCBs, and PAHs, and (3) high-efficiency and high-selectivity separation of environmental contaminants, at the Centers for Disease Control (CDC, USA) in cooperation with the toxicology unit of CDC.(1) Tetrachlorodioxin and coplanar PCBs in aqueous waste were readily trapped onto the surface of alkylated silica in quartz tubing, and underwent rapid photo-decomposition, when irradiated with UV ligh … More t from outside the tubing. The dioxin lost chlorine atoms from 2, 3, 7, or 8-positions that provide the toxicity to the dioxins. PCBs followed one major decomposition pathway among many possible routes. Coplanar PCBs with hexachloro and pentachloro substitution decomposed rapidly, while PCBs with four or less chlorine atoms showed slow decomposition. The products are relatively simple without formation of dioxins, that was suspected with incineration processes. Large-scale decomposition is the next objective.(2) Ordinary C18 silica was unable to elute all the proteins in serum, resulting in carry-over of hydrophobic contaminants. The use of restricted-access type packing materials was found to be essential. Group separations among dioxins, coplanar PCBs, nonplanar PCBs, and PAHs can be achieved by using a PAH-immobilized silica. The combination of restricted-access type and PAH-bonded stationary phase is expected to provide an automated sample pretreatment for GC/MS analysis of serum.(4) Alkyated starburst dendrimers provided excellent performance in EKC in a full range of water-methanol mixtures for the separation of hydrophobic compounds. Coupling of this EKC separation with MS is expected to produce a new high-sensitivity and high-speed method for environmental analysis. Generation of ultra-high efficiency was also examined by creating continuous porous silica columns. Progress in separation and decomposition methods of environmental contaminants by the chromatographic approach will provide an efficient evaluation method as well as a safe decomposition method of dioxins and PCBs that must be kept at the site of finding because of the lack of reliable decomposition methods at present. Less