ON-SITE REAL-TIME MONITORING OF DIOXINS AND RELATED COMPOUNDS

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We developed an analytical instrument for sensitive real-time monitoring of dioxins and investigated basic researches using this analytical instrument.The lifetimes of the electronic excited state of aromatic hydrocarbons containing many chlorine atoms such as dioxins are shortened by a spin-orbit interaction. As a result of this, the efficiency of multiphoton ionization is substantially reduced. In order to overcome this problem, it is necessary to use a laser whose pulsewidth is similar to the lifetime of the analyte molecule. This expectation was confirmed from both sides of theory and experiment. In this work, we developed a distributed-feedback dye laser having a picosecond pulsewidth and confirmed that a high ionization efficiency was obtained using this laser.In order to improve the sensitivity in dioxin analysis, it is desirable to use a mass spectrometer which allows efficient detection of ions induced by multiphoton ionization. A new type of mass spectrometer was designed in … More this study and performance expected was calculated using a SIMION software. We also constructed this mass spectrometer and confirmed experimentally to have sufficient performance for sensitive detection of dioxins and their precursors.In this work, we measured thermally decomposed ploducts of polyvinylchloride by supersonic jet spectrometry. It was found that no dioxin precursors are formed from polyvinylchloride, while a precursor of chlorobenzene is formed as a major product from chlorinated polyvinylchloride (polyvinylidene). We also investigated the reaction mechanism of dioxins induced from chlorophenols in the absence and presence of a catalyst of FeCl_3. An unexpected isomer of dioxin was found, which was formed through the "Smile Rearrangement". Real-time monitoring of s pecific isomer is difficult using a conventional mass spectrometer, and hence we could demonstrate the advantage of supersonic jet/multiphoton ionization/mass spectrometry over conventional mass spectrometry.Our proposal entitled, "Development of analytical instrument for on-line real-time monitoring of dioxins" was accepted by NEDO in the period of 2000-2002. The analytical instrument developed is scheduled to be commercialized from 2003. Less