Gas-Phase Absorption and Laser-Induced Fluorescence Measurements of Representative Polychlorinated Dibenzo-p-dioxins, Polychlorinated Dibenzofurans, and a Polycyclic Aromatic Hydrocarbon

Abstract

Dioxins and furans are believed to be among the most toxic chemicals known to man. The presence of these compounds in the emission gases of municipal solid waste incinerators and other combustion sources has raised debate over the location and the ultimate utility of incineration as an approach to waste management. Current methods used to measure dioxins and furans in combustion source emissions do not provide the real-time monitoring necessary to track average incinerator performance or upset emission levels. A study to design and develop a laser-induced fluorescence/continuous emission monitoring system to detect and quantify these compounds is being conducted. This paper reports the results of the study to date. Vapor-phase ultraviolet absorption spectra, absorption cross sections, and laser-induced fluorescence profiles are presented for three dioxins and two furans. These spectral data are needed for initial design and evaluation of the laser-induced fluorescence/continuous emission monitoring system approach.

Electronic transitions of fluorene, dibenzofuran, carbazole, and dibenzothiophene: From the onset of absorption to the ionization threshold

“…The band at around 297 nm can been assigned to a vibronic component of the lowest A 1 transition due to coupling with the lowest B 2 state [21,[39][40][41]. The assignments of three low energy B 2 transitions are similar to previous assignments [21,34,35].…”

“…Part of the discrepancy is most likely due to the importance of excited state geometry rearrangements, leading to substantial differences between vertical and adiabatic transitions energies, as recently demonstrated by Ljubic and Sabljic [38]. Moreover, previous analyses [39][40][41] have demonstrated the importance of vibronic coupling phenomena, indicating partial breakdown of the Born-Oppenheimer approximation. Hence, more advanced theoretical procedures are called for.…”

Analysis of Persistent Organic Pollutants at Sub-Femtogram Levels Using a High-Power Picosecond Laser for Multiphoton Ionization in Conjunction with Gas Chromatography/Time-of-Flight Mass Spectrometry

“…The LODs for the PCDFs were somewhat lower than those for PCDDs, probably due to the larger molar absorptivities for PCDFs at 258 nm. 34 For highly chlorinated PCDD/Fs, the LODs increased with increasing numbers of chlorine atoms, the tendency of which was more serious for ionization using a picosecond laser. This unfavorable result can be attributed to a decrease in the singlet-excited-state lifetime by a heavy atom effect.…”

Optical spectra and photophysical properties of polychlorinated dibenzo-p-dioxin derivatives

“…The UV absorption spectra of dioxins [S m (pp*) / S 0 ] have been studied in solution 2, 54 ± 57 and in the vapour phase. 58 Tables listing the absorption maxima and the molar extinction coefficients (e max ) have been reported; 2 the absorption curves for DD and its chloro-derivatives (b-TCDD, 1,2,3,7,8-Cl 5 DD and OCDD) can be found in several publications. 55,56,58 The absorption spectra of DD and PCDD occur in the region of 200 ± 350 nm and consist of two bands Ð a weak broad longwavelength band (A) in the region of 280 ± 320 nm with a maximum at *300 ± 304 nm and a short-wavelength narrow intense band (B) with a maximum at about *220 ± 240 nm.…”