Octachlorodibenzofuran Research Articles

A modeling approach on the PCDD/F pollution in surface sediments of the Izmit Bay (The Marmara Sea)

The paper presents a mass balance modeling study on the polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) pollution around the Izmit Bay region, the most industrialized province of Turkey, based on the evaluation of PCDD/Fs input to the bay and measured concentrations in the surface sediments. The pollution map showed that PCDD/F levels in the central section are much higher than those in the eastern and western basins. The model showed that OCDD levels could be explained mainly by the effect of atmospheric deposition processes whereas other dominant congeners i.e., Octachlorodibenzofuran (OCDF) and 1,2,3,4,6,7,8-Heptachlorodibenzofuran (1,2,3,4,6,7,8-HpCDF), observed in the surface sediment, should have another unknown sources. Assessment of the congener profiles of the industrial discharges in the recent studies showed that OCDF was related to the production of vinyl chloride monomer in the past, 1,2,3,4,6,7,8-HpCDF was attributed to unknown use of the chlorophenol-based fungicide. On the other hand, atmospheric OCDD could be explained by the effect of combustion-related PCDD/F emissions, and the use of pentachlorophenol (PCP) pesticide. In conclusion, the mass balance model results suggested that the industrial discharges in the past could be a significant contributor to the PCDD/F pollution in the sediments.

Simultaneous quantification of humic acid-water and silanized glass-water partition constants for PCBs, PCDDs and OCDF.

Super-hydrophobic organic contaminants (SHOCs) such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and octachlorodibenzofuran (OCDF) can sorb to dissolved hydrophobic materials including humic acids (HAs), enhancing their apparent aqueous solubility and potentially resulting in increased groundwater contamination and offsite transport. To manage risks associated with transport of and contamination by SHOCs, modelling approaches incorporating partitioning data, i.e. dissolved organic carbon-water partition constants (KDOC), are necessary. Measurement of KDOC can however be compromised by SHOC sorption to glassware surfaces leading to an overestimation of experimental values resulting in larger KDOC. A method for simultaneous derivation of KDOC and glass-water partition constants (KGW) is described. It involves a mass balance approach combined with HA as a co-solvent at various concentrations and accounts for SHOC losses to silanized glassware. Measured log KDOC values ranged from 5.28 to 7.64 for tetra- to decachlorinated PCBs, 6.67 to 7.93 for tetra- to octachlorinated PCDDs and 8.20 for OCDF. These data were linear functions of log KOW and consistent with relationships reported for more polar compounds. Log KGW (mm3 mm-2) values (1.62 to 4.06 for PCBs, 2.96 to 3.90 for PCDDs, 3.77 for OCDF) were one order of magnitude greater compared to literature PCB borosilicate glass-water partition constants. Techniques such as those presented in this work present simple, versatile means to provide prediction of the SHOC proportion remaining in aqueous solutions after loss to glassware that was inversely related to container surface area/volume ratio and log KOW in our study.

Thermal oxidation of dieldrin and concomitant formation of toxic products including polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F)

This paper examines the gas phase thermal decomposition of dieldrin and associated formation of toxic combustion products including polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F). Volatile Organic Carbon (VOC) analysis revealed the formation of pentachlorostyrene (PCS), hexachlorostyrene (HCS) and polychlorinated naphthalene as toxic combustion products generated during the combustion of dieldrin. The thermal pyrolysis of dieldrin resulted in the formation of chlorinated benzenes and chlorinated phenols, which are known PCDD/F precursors. The formation of PCDD/F commenced around 823 K @ 5s residence time and results indicate a preference for the formation of PCDF over PCDD under all experimental conditions studied. Subsequent experiments, to examine the yield of PCDD/F as a function of temperature, reveal the progressive chlorination of PCDD/F with temperatures up to 923 K. Octachlorodibenzofuran (OCDF) was the major dioxin congener detected in the oxidation of dieldrin. The highest toxicity factor for dioxin formation was recorded at 923 K with a 6% O2 content in the feed gas and corresponds to 6.24 ng TEQ WHO 2005/mg of dieldrin and total PCDD/F concentration of 96.8 ng/mg of dieldrin.

Dechlorination comparison of octachlorodibenzofuran over ball-milled zero-valent magnesium with and without activated carbon in different solvent systems

Polychlorinated dibenzofurans (PCDFs) are a class of highly toxic organic compounds that have been detected in all compartments of the ecosystem. In this research, a novel method using ball-milled ZVMg and ZVMg with activated carbon in acidified ethanol and acidified 2-butoxyethanol solvents has been applied to investigate reductive dechlorination of the selected PCDF congeners under ambient conditions. Octachlorodibenzofuran (OCDF) was chosen as a model for high-chlorinated congeners and 2,8-dibenzofuran was chosen as a model for low-chlorinated congeners. Both congeners were degraded efficiently in all systems. The addition of activated carbon enhanced the degradation kinetics for both congeners. Complete conversion of OCDF to dibenzofuran, the chlorine-free compound was achieved by ball-milled ZVMg in ethanol. When 2-butoxyethanol was used, the final products were dichlorodibenzofuran as well as dibenzofuran. Complete kinetic studies were conducted for the high- and low-chlorinated congeners. The results demonstrate that the reactions follow pseudo- first order kinetics with respect to analyte degradation for all systems studied. A degradation pathway for the dechlorination of OCDF is proposed. Overall, this technology is promising as part of a remediation option for PCDF contaminants.

Effect of reducing agent on catalytic hydrodechlorination of aqueous-phase OCDD/F

Removal/destruction of aqueous-phase octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) via hydrodechlorination process (HDC) is experimentally evaluated over palladium/activated carbon (Pd/AC) catalyst. Pd catalyst is mainly used as active component for effectiveness in removing dioxin from wastewater. Studies on the removal of PCDD/Fs accomplished with HDC reaction in aqueous phase are limited and the influencing factors have not been clarified. In this study, high-concentration OCDD/F are selected as targets, and the effects of solvent and operating temperature on dechlorination efficiency are investigated via experimental tests. The results indicate that the highest hydrodechlorination efficiency is achieved with isopropanol as solvent. The OCDD/F removal efficiency achieved with the solution of 80% isopropanol is higher than that of 50% isopropanol, whereas the destruction efficiency of OCDD/F reveals the opposite trend. Generally, the removal and destruction efficiencies of PCDFs are higher than those of PCDDs. In addition, the activation energies of OCDD and OCDF are calculated with the Arrhenius equation as 24.8 and 23.1 kJ/mol, respectively. Stability tests are conducted with three cycles. Overall, the results indicate that a high performance (≥99%) can be achieved by combining hydrodechlorination with Pd/AC at a temperature range of 303–353 K, demonstrating that Pd/AC has good potential for removing PCDD/Fs from wastewater.

Catalytic decomposition of gaseous PCDD/Fs over V2O5/TiO2-CNTs catalyst: Effect of NO and NH3 addition

There is a strong need for a control technology that simultaneously achieving the abatement of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) and nitrogen oxides (NOx) emissions in waste incineration industry. TiO2 and carbon nanotubes (CNTs) were used as composite carriers to support vanadium oxide as an innovative catalyst to simultaneously control PCDD/Fs and NO emissions. The removal efficiencies (RE) of PCDD/Fs by V2O5/TiO2-CNTs catalyst under a space velocity (SV) of 20,000 h−1 reaches 99.9% at 150 °C and adsorption is supposed to be the main mechanism at this temperature. The influence of NONH3 reaction on PCDD/Fs catalytic reaction is investigated. The kinetics analysis exhibits that the addition of NO and NH3 reduces the activation energies for OCDD (octachlorodibenzo-p-dioxin) and OCDF (octachlorodibenzofuran) decomposition to 3.6 kJ/mol and 5.4 kJ/mol respectively.

Formation and potential mechanisms of polychlorinated dibenzo-p-dioxins and dibenzofurans on fly ash from a secondary copper smelting process.

Secondary copper smelting (SeCu) is widely considered to be an important source of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs and PCDFs; PCDD/Fs). Laboratory experiments were performed using SeCu fly ash as a matrix for thermochemical reactions to investigate the effects of fly ash on the formation of PCDD/Fs and the potential mechanisms. Thermochemical reactions on SeCu fly ash over a temperature range of 250-450°C and reaction times of 10-120min caused the PCDD/F concentrations in the fly ash to increase significantly. The PCDD/F concentrations formed in the thermal reactions were about 99-139 times higher than the PCDD/F concentrations in the original fly ash, clearly indicating that fly ash promoted the formation of PCDD/Fs. The PCDFs dominated the PCDDs, and the PCDF/PCDD concentration ratio was about 30-40. Octachlorodibenzofuran (OCDF), octachlorodibenzo-p-dioxin, and the heptachlorodibenzofurans were the most dominant homologs that were formed. A comparison of the PCDD/F patterns produced in the thermochemical reactions and the patterns in the original fly ash suggested that the chlorination of less chlorinated PCDFs might be an important pathway in the formation of higher chlorinated furans. The results of this study indicated that SeCu fly ash has a high PCDD/F formation potential. It is crucial to have the fly ash filter at low temperature and that fly ash in the cooling system should be minimized.

Dioxin-like PCBs and PCDD/Fs in surface sediments near the shore of Winam Gulf, Lake Victoria

Winam Gulf of Lake Victoria is considered to be contaminated with toxic chemicals emanating from anthropogenic activities, especially near large industrial towns such as Kisumu. This has recently caused concerns about its water quality and impact on aquatic organisms and human beings. This study was justified by the need to generate baseline concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in surface sediment from selected sites in the lake and determine the influence of activities on their concentrations and potential risks to fish-eating birds living near the lake. Surface sediments (<30cm) from three different fish landing beaches, located 200m from the shore of Winam Gulf of Lake Victoria near Kisumu city, Homa Bay and Mbita (control) towns, were analysed. The total mean concentrations (in pgg−1drywt) were found to range from 17.4–812 (Σdl-PCBs), 36.6–813 (ΣPCDDs) and 1.45–46.4 (ΣPCDFs). The calculated Toxic Equivalents (TEQWHO(2005)) ranged from 0.001–0.43 (Σdl-PCBs) and 0.09–31 (ΣPCDD/Fs). The fish landing beaches at Kisumu city were found to be contaminated with respect to dl-PCBs and dioxins, followed by Homa Bay and Mbita. The relatively high levels of octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) influenced the TEQ and the ΣPCDFs/ΣPCDDs ratios indicated chemical processes as partial sources of the dioxins. The levels of contaminants obtained in this study showed potential exposure to aquatic organisms and fish eating birds through food chain transfer.

Pyrosequencing analysis reveals high population dynamics of the soil microcosm degrading octachlorodibenzofuran.

A deeper understanding of the microbial community structure is very important in bioremediation for polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs). However, this has been insufficiently addressed in previous studies. To obtain more information, we pyrosequenced the V4/V5 regions of the 16S rRNA genes of bacterial communities transited from polluted soil to batch microcosms that rapidly degraded high concentrations of octachlorodibenzofuran (OCDF). The analysis results contained an average of 11,842 reads per sample, providing the first detailed description of bacterial communities associated with PCDD/Fs. The community composition markedly changed to be concomitant with the degradation of OCDF, indicating that a distinctive population structure developed rapidly in the microcosm. Although oxygen gas was provided weekly to the microcosm, the growth of potential degraders, Sphingomonas, Pseudomonas, Rhodococcus, and Clostridium, was observed, but in consistently low quantities. While anaerobic Sedimentibacter initially emerged as an abundant pioneer, several aerobic participants, such as the genera Brevundimonas, Pseudoxanthomonas, and Lysobacter, exhibited a large increase in their 16S rRNA gene copies within the timeframe, which showed a temporal population dynamic, and indicated their collaborative contributions to the degradation of OCDF under hypoxic conditions. These results have provided a deeper insight into the microbial community structure and population dynamics of the OCDF-degrading microcosm.

Analytical Method Development for the Screening and Determination of Dioxins in Clay Matrices

Dioxin‐contaminated kaolin receives great attention by workers in the fields of environmental science, soil geology, and mining, due to its impact on the areas of health and business. The concept of “natural dioxin” formation in the clay attracts researchers to look for dioxins quantities in these soils and establish the actual route of their formation, as already proved their presence in large unjustified quantities in a number of kaolinitic soil sources and in a unique profile that denies any anthropogenic sources. On the other hand, other researches revealed the absence of dioxins in other kaolinitic sources. For rapid screening of dioxins presence an analytical method was developed basically for the determination of octachlorodibenzo‐p‐dioxin (the major dioxin congener in dioxin‐contaminated kaolin) and octachlorodibenzofuran (does not exist in dioxin‐contaminated kaolin). The method was considered as a rapid, selective, accurate and sensitive method for screening octachlorodibenzo‐p‐dioxin (OCDD) and octachlorodibenzofuran (OCDF). The method achieved linearity for OCDD/F over the range 126.5–6144.0 ng/kg dry weight (dw) with limit of quantitation of 76 ng/kg dw for OCDD and 111 ng/kg dw for OCDF. The precision (RSD%) ranged between 1.87 and 8.09% for OCDD and between 3.93 and 9.48% for OCDF. Recovery was between 85.5 and 91.1% for OCDD and between 57.9 and 64.1% for OCDF, while the accuracy for OCDD ranged from 93.8 to 97.8% and from 102.9 to 125.1% for OCDF. The developed analytical method in this research is a good alternative for known methods, because it saves time, effort, supplies, and equipments for chemical analysis. It shortens the analysis time to less than a quarter (6 h) and need less chemicals. Also it is suitable for work on a normal resolution GC/MS rather than high resolution one.

A new alternative paraffinic–palmbiodiesel fuel for reducing polychlorinated dibenzo-p-dioxin/dibenzofuran emissions from heavy-duty diesel engines

Polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) emissions from heavy-duty diesel engines (HDDEs) fuelled with paraffinic–palmbiodiesel blends have been rarely addressed in the literature. A high-resolution gas chromatograph/high-resolution mass spectrometer (HRGC/HRMS) was used to analyze 17 PCDD/F species. Experimental results indicate that the main species of PCDD/Fs were OCDD (octachlorinated debenzo-p-dioxin) and OCDF (octachlorodibenzofuran), and they accounted for 40–50% of the total PCDD/Fs for all test fuels. Paraffinic–palmbiodiesel blends decreased PCDD/Fs by 86.1–88.9%, toxic PCDD/Fs by 91.9–93.0%, THC (total hydrocarbons) by 13.6–23.3%, CO (carbon monoxide) by 27.2–28.3%, and PM (particulate matter) by 21.3–34.2%. Using biodiesel blends, particularly BP9505 or BP8020, instead of premium diesel fuel (PDF) significantly reduced emissions of both PCDD/Fs and traditional pollutants. Using BP9505 (95 vol% paraffinic fuel + 5 vol% palmbiodiesel) and BP8020 instead of PDF can decrease PCDD/F emissions by 5.93 and 5.99 g I-TEQ year −1 in Taiwan, respectively.

Benthic Bioaccumulation and Bioavailability of Polychlorinated Dibenzo- p-Dioxins/Dibenzofurans from Surficial Lake Ontario Sediments

The benthic bioavailability of surface sediment-associated polychlorinated dibenzo- p-dioxins/dibenzofurans (PCDD/Fs) was quantified and assessed in Lake Ontario. Bottom sediments were collected from three areas along the Lake Ontario southern shoreline near Olcott, Rochester, and Oswego, New York. The sediment samples were subjected to 28-day, PCDD/F bioaccumulation experiments using the aquatic oligochaete Lumbriculus variegatus. Empirical data including only detectable PCDD/F tissue residues were used to quantify the benthic bioavailability of 11 PCDD/F congeners through the calculation of biota-sediment accumulation factors (BSAFs). BSAFs calculated for at least two lake areas were combined as Lake Ontario BSAFs for those specific congeners. Variability of the BSAFs was estimated by propagated error (PE) terms. Mean Lake Ontario BSAFs (±PE) ranged from 0.04±0.02 for octachlorodibenzofuran (OCDF) to 2.42±1.32 for 1,2,3,6,7,8-hexachlorodibenzofuran (HxCDF). Tetrachlorodibenzo- p-dioxin (TCDD) and 1,2,3,4,7,8-HxCDF, shown to be among the highest toxic equivalencies (TEQs) in lake sediments, yielded BSAFs of 0.51±0.18 and 0.22±0.12, respectively. Statistical comparison of the TCDD BSAFs showed no significant differences among the lake areas. The benthic bioavailability of TCDD appeared lower than the results of other investigators. While hydrophobicity and degree of chlorination play some role, other factors, such as steric properties, and composition of organic carbon and matter, may have had a greater influence on the benthic bioavailability of PCDD/F congeners. Comparisons of these benthic BSAFs to fish BSAFs suggest that the bioaccumulation of PCDD/F congeners by fish is more related to water solubility and degree of chlorination than to sediment concentration.

Photodechlorination of octachlorodibenzothiophene and octachlorodibenzofuran: Comparison of experimental degradation pathways with degradation pathways predicted by DFT

Polychlorodibenzothiophenes (PCDTs) are sulfur analogues of polychlorodibenzofurans (PCDFs) and have been detected in environmental samples. We used density functional theory calculations (Gaussian 98W) to predict the photodechlorination pathways of octachlorodibenzothiophene (OCDT) and octachlorodibenzofuran (OCDF) in hexane, and we compared the predicted pathways with those observed during UV irradiation experiments. OCDT and OCDF were observed to degrade through first-order dechlorination processes, and the rate constant for OCDT was less than one-third that for OCDF. The main experimental photodechlorination pathways of OCDT and OCDF led to hexachlorinated and tetrachlorinated congeners, respectively; that is, the photodechlorination pathway of OCDT differed from that of OCDF. On the assumption that the dechlorination mechanisms involved radical reactions, we used DFT calculations to estimate bond-dissociation energies and single-point energies of OCDT and OCDF and their dechlorinated congeners, and we used the resulting information, along with hypotheses regarding the rate-controlling step of the degradations, to predict theoretical degradation pathways. We propose that reaction of dechlorinated radicals with a hydrogen donor was the rate-controlling step for OCDT and that C–Cl bond dissociation by UV light was the rate-controlling step for OCDF.

Analysis of Polychlorinated Dibenzo-p-dioxins and Dibenzo-furans in Sanitary Products of Women

To dissolve and develop the analytical methods for native polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in sanitary products, we collected sanitary napkins from Korea (K1, K2, K3), Japan (J1, J2, J3), USA (U1, U2, U3), Germany (G1, G2) and China (C1, C2), and tampons from Korea (TK), Japan (TJ1, TJ2) and USA (TU1, TU2, TU3). PCDDs and PCDFs in sanitary products were determined by HRGC/HRMS. Experimental methods consisted of comparison of extracting solvents toluene and a mixture of hexane/dichloromethane (1/1), and analysis of PCDD/Fs in sanitary products. In extracting solvent experiments with K1 and K2, octachlorinated dioxin (OCDD), hexachlorodibenzofuran (HxCDF) and octa-chlorodibenzofuran (OCDF) were detected. The recoveries of sampling standard and clean-up standard in extract of hexane/dichloromethane (1/1) were higher than extract of toluene. From the results of analysis of PCDD/Fs in sanitary napkins, no noxious materials were detected in one from Korea (K3) and three from USA (U1, U2, U3) among the tested samples with our test method. OCDD, 1,2,3,4,7,8-HxCDF and 1,2,3,6,7,8-HxCDF were detected in all the kinds of tampon tested. The concentrations of PCDD/Fs in tampon samples were similar to that in sanitary napkins.

Theoretical Study of Structure, Vibrational Frequencies, and Electronic Spectra of Dibenzofuran and Its Polychlorinated Derivatives

Minimum structures and harmonic vibrational frequencies of dibenzofuran (DF), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and octachlorodibenzofuran (OCDF) were calculated using the multiconfigurational complete active space self-consistent field (CASSCF) and density functional theory (DFT) methods. The electronic transitions in these compounds were studied via the single-state multireference second-order perturbation theory (CASPT2) based on the CASSCF(14,13) references, as well as the time-dependent DFT (TD-B3P86) employing the cc-pVDZ (CASSCF/CASPT2) and 6-31G(d,p) (TD-B3P86) basis sets. The B3P86 geometry and harmonic vibrational frequencies of ground state DF agree very well with the experimental data, and the CASSCF/CASPT2 excitation energies and oscillator strengths are accurate enough to provide a reliable assignment of the absorption bands in the 200-300 nm region. The close agreements with experiment for the parent DF give the present theoretical approaches a valuable credit in predicting the properties of the environmentally toxic polychlorinated congeners, which is all the more important considering the difficulties and hazards in obtaining the experimental data.

Radiolytic degradation of octachlorodibenzo-p-dioxin and octachlorodibenzofuran in organic solvents and treatment of dioxin-containing liquid wastes

Degradations of octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) were studied by 60Co γ-ray in organic solvents: ethanol, n-nonane, and toluene. Both OCDD and OCDF were degraded more efficiently in ethanol than in n-nonane or toluene. The degradation is mainly attributed to electrons and in part to solvent radicals. The addition of ethanol to dioxin-containing liquid wastes enhanced effectively the degradation of dioxins; the liquid wastes did not exhibit the dioxin toxicity at a dose of 100kGy.

Modelling the long-term fate of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) in the Grenland Fjords, Norway

The development and application of a predictive fate model (DIG — Dioxins in Grenland) for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in the marine environment of the Norwegian Grenland Fjords are described. The objective of the modelling study was to predict long-term future changes in PCDD/F concentrations in the fjord following the cessation of point source emissions. To assess the reliability of the model, the model performance was evaluated by comparing model results to field measurements collected between 1989 and 2001. Model bias (defined as the ratio of median predicted concentration and median observed concentration) for prediction of concentrations for three different PCDD/F congeners (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 1,2,3,6,7,8-hexadibenzofuran (HxCDF) and octachlorodibenzofuran (OCDF)) in the fjord was between 0.53 and 24, which was deemed a satisfactory result for models of this type. The model was run to determine the dynamic change in concentrations between 1950 and 2050 and to examine the key fluxes of PCDD/Fs in the fjord. Between 1990 and 2050 sediment concentrations of TCDD, HxCDF and OCDF were predicted to fall at fairly constant but gradually slowing rates to concentrations 52, 98 and 88 times lower, respectively, of their 1990 values. Losses of PCDD/Fs from the bottom sediments in the Frierfjord were predicted to be a combination of sediment burial and net resuspension to the water column. Sediment burial was shown to be relatively more important in the fjord's deep-water sediments, whereas resuspension was relatively more important in the shallow sediments. For the shallower sediments, a net water-to-sediment flux was predicted for all three congeners up until the mid-1970s, when emission reductions were initiated, and thereafter a net sediment-to-water flux was predicted. The shallow sediments acted as net sources to the deeper sediments and to the fishing areas in the outer fjord.

Elucidation of Degradation Mechanism of Dioxins during Mechanochemical Treatment

Model dioxin compounds 4-chlorobiphenyl (4CB), octa-chlorodibenzo-p-dioxin (OCDD), and octachlorodibenzofuran (OCDF) were degraded by a mechanochemical (MC) process that involved milling with calcium oxide by use of a planetary ball mill. The degradation of 4CB produced mainly chloride ions and biphenyl, with the chlorine removal efficiency reaching about 100%. Biphenyl was transformed into terphenyls, quaterphenyls, cyclohexylbenzene, and bicyclohexyl through polymerization and hydrogenation reactions. Measurements of chloride ions after MC treatment of OCDD and OCDF showed about 100% dechlorination of both compounds; tetra- to heptachlorinated dibenzo-p-dioxins/furans (T4-H7CDD/Fs) were detected only at trace levels, and no other chlorinated organic compounds were observed. The residue after MC treatment was gray in color, indicating the possibility of carbonization, but the presence of amorphous graphite could not be confirmed.

Determination of the vapor pressures of select polychlorinated dibenzo-p-dioxins and dibenzofurans at 75–275 °C

Vapor pressures were determined for several polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) at 75–275 °C, extending the available literature data to more relevant temperature regions and providing the first experimental data for 2,3,7-trichlorodibenzo-p-dioxin (2,3,7-TriCD). A modification of the effusion technique, based upon controlling the diffusion of the target compound and subsequent high resolution gas chromatography/low resolution mass spectrometry (HRGC/LRMS) analysis, was proven comparable to other accepted methods for determining the vapor pressures of semi-volatile organic compounds (SVOCs). Vapor pressures for octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) were in excellent agreement with those reported in literature. The application of the current method for the vapor pressure determinations of eight polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/PCDFs) in the extended temperature range (up to 275 °C) is reported. The extension of the vapor pressures to such temperatures, unprecedented for the PCDDs/Fs, is important for vapor-particle partitioning modeling in regions relevant to PCDD/F formation and control. Estimates for the melting temperatures and enthalpies of sublimation and vaporization are also reported, the latter for which no experimentally determined values have been found in the literature. The use of the method to deliver reproducible, trace concentrations (ppt–ppb) of targets was applied to the calibration of the jet-REMPI/TOFMS as an online detector for low chlorinated PCDDs/Fs.

Fast matrix digestion with hot ethanolic alkali plus pyrogallol for polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls analysis in biological samples

The efficiency of hot alkaline digestion of a sample matrix was investigated for determination of polychlorinated dibenzo- p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (CoPCBs) in biological samples. Results of recovery tests of octachlorodibenzofuran (OCDF) after spiking into lean tuna showed degradation of OCDF and the production of a large quantity of lower-chlorinated dibenzofurans (LoCDFs) when the sample was digested with hot ethanolic KOH. However, it was also confirmed that pyrogallol (PG) prevented dechlorination of OCDF. The accuracy of the hot alkaline digestion method with PG was demonstrated by analyzing PCDD/Fs-spiked lean tuna. The proposed method is more suitable than conventional versions for the determination of dioxins in biological samples in terms of savings in time, adequate digestion of matrix and high degree of recovery of internal standards.